Which Free Icon/Glyph Library?

[nelsonic]

So far in our App prototype we've been using these icons: https://www.material.io/resources/icons
The project is maintained by people who work for Google https://github.com/material-components
and the SVG icons appear to be well optimised:

The actual SVG file is tiny and we could very easily make a template from it to allow custom UI themes.

I don't know if SVG icons are going to be feasible in our App if we want to support older devices/browsers, but support is good all the way back to IE9: https://caniuse.com/#search=svg

We're very open to suggestions on alternative Icon Libraries. 💬
In the past we've used fontawesome.com/icons | flaticon.com/free-icons | thenounproject.com
We'd love to know which one is objectively "better" or if it's just a matter of personal preference? 💭