It's amazing how they weren't satisfied with fucking up their desktop app so they went and fucked up the best open source mobile app (K9 Mail) as well.
There are sooo many. The unified search bar and new menu systems is weird if you updated from previous releases. It's improved somewhat and is still usable I guess, but not great. Loading a single ics event now opens up an entire import wizard. If you open up the advanced search, search by message bodies doesn't show up unless you click on "search on server" first ... which I guess makes some sense, but at first glance, it seems like there's no way to search on the server ... and you need that because the default search doesn't go into certain subfolders with messages older than an arbitrary date or folder size (I don't know what that arbitrary limit is either).
I don't use e-mail that much anymore honestly, but I'm considering trying BetterBird: https://www.betterbird.eu/
I switched from Firefox to Librewolf over a year ago and I like it a lot better. Mozilla is fallen quite far from where it was. I remember the day I first tried Firebird, the scaled down version of Mozilla (the open sourced Netscape Communicator Suite). There was a lot of hope and excitement in the open source world back then. That's mostly all gone now, and we're stuck with drama between potatophiles like Drew DeVault vs RMS. Distros refusing to package Hyprland because they believe actionally defamatory statements from narcissistic loliphiles. Developers who have been long time contributors for massive projects, removed from credits due to their nationality and international sanctions.