Consider making all closures static

[knutsp]

From
add_filter('some_filter', function ($params...) { }
To:
add_filter('some_filter', static function ($params...) { }

Similar for add_action with closure.
In case the magic instance variable $this is not needed inside it.

This avoids the closures to bind to each instance, probably a bit less memory and maybe a bit faster, especially in frequently instantiated classes (I think).

Also consider using named functions in case it may be useful for other (site specific) plugins to completely remove the action or filter.