Firefox v89 was the last version I used. I just couldn't be bothered with them constantly changing and removing features for no reason. I switched to Vivaldi, which offer basic functionality like vertical tabs, and a fully customisable UI out of the box. It's far from perfect, notably being closed source which was hard for me to swallow, but it annoys me far less than Firefox ever did. I have it set up how I like it, and that setup has stayed static in the three years I've used it now. Firefox frankly feels user hostile in comparison.

Thunderbird was ruined with version 115, so I switched to Kmail. I miss calendar integration in my email client though.