I play overwatch on endeavouros and I have better experience on it than in windows. League of legends will stop working soon. In general most of the games with rootkit anticheat clients will not work on Linux. On protondb you can see rankings and user comments about games. Last I checked 2% of all games are not working on Linux.
Linux gaming is a thing. Lutris and steam are working quite well. In some games I have better performance than windows. That being said not everything is working, some games are not working at all and other games have quite some settings and fiddling until they work. Check protondb where you can see users comments and game compatibility ranking for the games you play. Sometimes I want to go back to windows, but for the last 5 months I’ve booted windows once or twice. There is a learning curve and getting used to Linux, but in my opinion it is worth it. If you want to transition from windows don’t go with gnome. Start with kde or xfce, or cinnamon.
What could work is to impose a daily progressing fine until the firmware change Is reversed and 3rd party ink Is allowed again.
I have tried kmail, Geary, mailspring before I landed on betterbird. I’m not sure what you mean with slow, but it works without issues on my pc. It does a lot of stuff, but it’s a fork of Thunderbird, which you want to exclude based on the initial thread. There are not a lot of linux clients even worth trying. Good luck finding your jam.