Same here. I prefer to avoid Chromium-based browsers whenever I can. A lot of them are better than Chrome, and I do like to mess with them from time to time to stay aware of features and test things. But Firefox on my phone has access to uBlock Origin and all my other extensions, after activating the hidden debug menu/dev mode that you turn on in a similar way as activating Dev Mode for the Android OS. I only mention that last part because it seems a lot of FF Android users don’t know about it and allows for installing xpi files just like you can with desktop. Freaking game changing for me. It really sucks that the main-line Chromium-based browsers don’t support extensions, even in the limited options way FF used to before allowing more to officially work (even without the debug menu/dev mode trick.

For those that might want the instructions for the hidden debug menu/dev mode. Some extensions still might not work correctly as they might not play nice with the UI/layout of the Android version. I would imagine that some of these might be things like the third-party tab-tree extensions for example.

Open Firefox App

Go to the settings menu.

Enable Developer Settings: You need to tap on the Firefox logo five times. This action will unlock an additional debug menu.

Find “Install extension with a file” option in Settings

Look for the option to install an extension from your own storage. And pick the xpi file. Also will just work using the extensions page on the FF site.