diff --git a/sopel/builtins/dice.py b/sopel/builtins/dice.py
index 40f0bfde7..bdfefd550 100644
--- a/sopel/builtins/dice.py
+++ b/sopel/builtins/dice.py
@@ -244,7 +244,7 @@ def _roll_dice(dice_match: re.Match[str]) -> DicePouch:
 @plugin.example(".roll 2d10+3", user_help=True)
 @plugin.example(".roll 1d6", user_help=True)
 @plugin.output_prefix('[dice] ')
-def roll(bot: SopelWrapper, trigger: Trigger):
+def roll(bot: SopelWrapper, trigger: Trigger) -> None:
     """Rolls dice and reports the result.
 
     The dice roll follows this format: XdY[vZ][+N][#COMMENT]
diff --git a/sopel/builtins/safety.py b/sopel/builtins/safety.py
index 0522f54bf..bf47e7d6f 100644
--- a/sopel/builtins/safety.py
+++ b/sopel/builtins/safety.py
@@ -56,7 +56,7 @@ class SafetySection(types.StaticSection):
     """Optional hosts-file formatted domain blocklist to use instead of StevenBlack's."""
 
 
-def configure(settings: Config):
+def configure(settings: Config) -> None:
     """
     | name | example | purpose |
     | ---- | ------- | ------- |
@@ -90,7 +90,7 @@ def configure(settings: Config):
     )
 
 
-def setup(bot: Sopel):
+def setup(bot: Sopel) -> None:
     bot.settings.define_section("safety", SafetySection)
 
     if bot.settings.safety.default_mode is None:
@@ -166,7 +166,7 @@ def download_domain_list(bot: Sopel, path: str) -> bool:
     return True
 
 
-def update_local_cache(bot: Sopel, init: bool = False):
+def update_local_cache(bot: Sopel, init: bool = False) -> None:
     """Download the current malware domain list and load it into memory.
 
     :param init: Load the file even if it's unchanged
@@ -202,7 +202,7 @@ def update_local_cache(bot: Sopel, init: bool = False):
     bot.memory[SAFETY_CACHE_LOCAL_KEY] = unsafe_domains
 
 
-def shutdown(bot: Sopel):
+def shutdown(bot: Sopel) -> None:
     bot.memory.pop(SAFETY_CACHE_KEY, None)
     bot.memory.pop(SAFETY_CACHE_LOCAL_KEY, None)
     bot.memory.pop(SAFETY_CACHE_LOCK_KEY, None)
@@ -211,7 +211,7 @@ def shutdown(bot: Sopel):
 @plugin.rule(r'(?u).*(https?://\S+).*')
 @plugin.priority('high')
 @plugin.output_prefix(PLUGIN_OUTPUT_PREFIX)
-def url_handler(bot: SopelWrapper, trigger: Trigger):
+def url_handler(bot: SopelWrapper, trigger: Trigger) -> None:
     """Checks for malicious URLs."""
     mode = bot.db.get_channel_value(
         trigger.sender,
@@ -365,7 +365,7 @@ def virustotal_lookup(
 @plugin.example(".virustotal https://malware.wicar.org/")
 @plugin.example(".virustotal hxxps://malware.wicar.org/")
 @plugin.output_prefix("[safety][VirusTotal] ")
-def vt_command(bot: SopelWrapper, trigger: Trigger):
+def vt_command(bot: SopelWrapper, trigger: Trigger) -> None:
     """Look up VT results on demand."""
     if not bot.settings.safety.vt_api_key:
         bot.reply("Sorry, I don't have a VirusTotal API key configured.")
@@ -421,7 +421,7 @@ def vt_command(bot: SopelWrapper, trigger: Trigger):
 @plugin.command('safety')
 @plugin.example(".safety on")
 @plugin.output_prefix(PLUGIN_OUTPUT_PREFIX)
-def toggle_safety(bot: SopelWrapper, trigger: Trigger):
+def toggle_safety(bot: SopelWrapper, trigger: Trigger) -> None:
     """Set safety setting for channel."""
     if not trigger.admin and bot.channels[trigger.sender].privileges[trigger.nick] < plugin.OP:
         bot.reply('Only channel operators can change safety settings')
@@ -455,7 +455,7 @@ def toggle_safety(bot: SopelWrapper, trigger: Trigger):
 # Clean the cache every day
 # Code above also calls this if there are too many cache entries
 @plugin.interval(24 * 60 * 60)
-def _clean_cache(bot: Sopel):
+def _clean_cache(bot: Sopel) -> None:
     """Cleans up old entries in URL safety cache."""
 
     update_local_cache(bot)
diff --git a/sopel/builtins/units.py b/sopel/builtins/units.py
index 02316339a..31b61e634 100644
--- a/sopel/builtins/units.py
+++ b/sopel/builtins/units.py
@@ -9,10 +9,16 @@
 from __future__ import annotations
 
 import re
+from typing import Pattern, TYPE_CHECKING
 
 from sopel import plugin
 
 
+if TYPE_CHECKING:
+    from sopel.bot import SopelWrapper
+    from sopel.trigger import Trigger
+
+
 PLUGIN_OUTPUT_PREFIX = '[units] '
 
 find_temp = re.compile(r'(-?[0-9]*\.?[0-9]*)[ °]*(K|C|F)', re.IGNORECASE)
@@ -20,23 +26,23 @@
 find_mass = re.compile(r'([0-9]*\.?[0-9]*)[ ]*(lb|lbm|pound[s]?|ounce|oz|(?:kilo|)gram(?:me|)[s]?|[k]?g)', re.IGNORECASE)
 
 
-def f_to_c(temp):
+def f_to_c(temp: float) -> float:
     return (float(temp) - 32) * 5 / 9
 
 
-def c_to_k(temp):
+def c_to_k(temp: float) -> float:
     return temp + 273.15
 
 
-def c_to_f(temp):
+def c_to_f(temp: float) -> float:
     return (9.0 / 5.0 * temp + 32)
 
 
-def k_to_c(temp):
+def k_to_c(temp: float) -> float:
     return temp - 273.15
 
 
-def _extract_source(pattern, trigger) -> tuple[str, ...]:
+def _extract_source(pattern: Pattern, trigger: Trigger) -> tuple[str, ...]:
     match = pattern.match(trigger.group(2))
     if match:
         return match.groups()
@@ -49,7 +55,7 @@ def _extract_source(pattern, trigger) -> tuple[str, ...]:
 @plugin.example('.temp 100C', '100.00°C = 212.00°F = 373.15K')
 @plugin.example('.temp 100K', '-173.15°C = -279.67°F = 100.00K')
 @plugin.output_prefix(PLUGIN_OUTPUT_PREFIX)
-def temperature(bot, trigger):
+def temperature(bot: SopelWrapper, trigger: Trigger) -> int | None:
     """Convert temperatures"""
     try:
         source = _extract_source(find_temp, trigger)
@@ -71,7 +77,7 @@ def temperature(bot, trigger):
 
     if kelvin <= 0:
         bot.reply("Physically impossible temperature.")
-        return
+        return None
 
     bot.say("{:.2f}°C = {:.2f}°F = {:.2f}K".format(
         celsius,
@@ -79,6 +85,8 @@ def temperature(bot, trigger):
         kelvin,
     ))
 
+    return None
+
 
 @plugin.command('length', 'distance')
 @plugin.example('.distance 3m', '3.00m = 9 feet, 10.11 inches')
@@ -92,7 +100,7 @@ def temperature(bot, trigger):
 @plugin.example('.length 3 au', '448793612.10km = 278867421.71 miles')
 @plugin.example('.length 3 parsec', '92570329129020.20km = 57520535754731.61 miles')
 @plugin.output_prefix(PLUGIN_OUTPUT_PREFIX)
-def distance(bot, trigger):
+def distance(bot: SopelWrapper, trigger: Trigger) -> int | None:
     """Convert distances"""
     try:
         source = _extract_source(find_length, trigger)
@@ -160,10 +168,12 @@ def distance(bot, trigger):
 
     bot.say('{} = {}'.format(metric_part, stupid_part))
 
+    return None
+
 
 @plugin.command('weight', 'mass')
 @plugin.output_prefix(PLUGIN_OUTPUT_PREFIX)
-def mass(bot, trigger):
+def mass(bot: SopelWrapper, trigger: Trigger) -> int | None:
     """Convert mass"""
     try:
         source = _extract_source(find_mass, trigger)
@@ -199,3 +209,5 @@ def mass(bot, trigger):
         stupid_part = '{:.2f} oz'.format(ounce)
 
     bot.say('{} = {}'.format(metric_part, stupid_part))
+
+    return None
diff --git a/sopel/builtins/url.py b/sopel/builtins/url.py
index 283349635..941dae7ab 100644
--- a/sopel/builtins/url.py
+++ b/sopel/builtins/url.py
@@ -76,7 +76,7 @@ class UrlSection(types.StaticSection):
     """Enable requests to private and local network IP addresses"""
 
 
-def configure(config: Config):
+def configure(config: Config) -> None:
     """
     | name | example | purpose |
     | ---- | ------- | ------- |
@@ -111,7 +111,7 @@ def configure(config: Config):
     )
 
 
-def setup(bot: Sopel):
+def setup(bot: Sopel) -> None:
     bot.config.define_section('url', UrlSection)
 
     if bot.config.url.exclude:
@@ -140,7 +140,7 @@ def setup(bot: Sopel):
         bot.memory['shortened_urls'] = tools.SopelMemory()
 
 
-def shutdown(bot: Sopel):
+def shutdown(bot: Sopel) -> None:
     # Unset `url_exclude` and `last_seen_url`, but not `shortened_urls`;
     # clearing `shortened_urls` will increase API calls. Leaving it in memory
     # should not lead to unexpected behavior.
@@ -151,7 +151,7 @@ def shutdown(bot: Sopel):
             pass
 
 
-def _user_can_change_excludes(bot: SopelWrapper, trigger: Trigger):
+def _user_can_change_excludes(bot: SopelWrapper, trigger: Trigger) -> bool:
     if trigger.admin:
         return True
 
@@ -169,7 +169,7 @@ def _user_can_change_excludes(bot: SopelWrapper, trigger: Trigger):
 @plugin.example('.urlpexclude example\\.com/\\w+', user_help=True)
 @plugin.example('.urlexclude example.com/path', user_help=True)
 @plugin.output_prefix('[url] ')
-def url_ban(bot: SopelWrapper, trigger: Trigger):
+def url_ban(bot: SopelWrapper, trigger: Trigger) -> None:
     """Exclude a URL from auto title.
 
     Use ``urlpexclude`` to exclude a pattern instead of a URL.
@@ -220,7 +220,7 @@ def url_ban(bot: SopelWrapper, trigger: Trigger):
 @plugin.example('.urlpallow example\\.com/\\w+', user_help=True)
 @plugin.example('.urlallow example.com/path', user_help=True)
 @plugin.output_prefix('[url] ')
-def url_unban(bot: SopelWrapper, trigger: Trigger):
+def url_unban(bot: SopelWrapper, trigger: Trigger) -> None:
     """Allow a URL for auto title.
 
     Use ``urlpallow`` to allow a pattern instead of a URL.
@@ -273,7 +273,7 @@ def url_unban(bot: SopelWrapper, trigger: Trigger):
     'Google | www.google.com',
     online=True, vcr=True)
 @plugin.output_prefix('[url] ')
-def title_command(bot: SopelWrapper, trigger: Trigger):
+def title_command(bot: SopelWrapper, trigger: Trigger) -> None:
     """
     Show the title or URL information for the given URL, or the last URL seen
     in this channel.
@@ -313,7 +313,7 @@ def title_command(bot: SopelWrapper, trigger: Trigger):
 
 @plugin.rule(r'(?u).*(https?://\S+).*')
 @plugin.output_prefix('[url] ')
-def title_auto(bot: SopelWrapper, trigger: Trigger):
+def title_auto(bot: SopelWrapper, trigger: Trigger) -> None:
     """
     Automatically show titles for URLs. For shortened URLs/redirects, find
     where the URL redirects to and show the title for that.
@@ -475,7 +475,11 @@ def process_urls(
         yield URLInfo(url, title, parsed_url.hostname, tinyurl, False)
 
 
-def check_callbacks(bot: SopelWrapper, url: str, use_excludes: bool = True) -> bool:
+def check_callbacks(
+    bot: SopelWrapper,
+    url: str,
+    use_excludes: bool = True,
+) -> bool:
     """Check if ``url`` is excluded or matches any URL callback patterns.
 
     :param bot: Sopel instance