Thanks! That did it!

Or at least I don't know where to switch themes for GTK2.

No, I installed it with pacman on Arch. I tried to install https://aur.archlinux.org/packages/adwaita-dark for gtk2, but it is not working.

Nice. Thanks

Yes. Ordered a Corne. Will break of the outer column. And thanks for the correction. Updated the post

Yes that's what I am gonna try now. Thanks. Just don't know what to do with the two extra keys... ;)

Yes. Correct. I mixed it up again. I mean the vertical offset of course. Thanks for clarifying.

I didn't design the key layout though. It is this: https://neo-layout.org/Layouts/mine/

I designed it myself with some common best practice stuff. I love it: https://github.com/FearlessSpiff/reviung34-zmk-config/blob/feature/initial-config/config/boards/shields/reviung34/reviung34.keymap

It's my first unibody "Split". It's not as comfortable but I like the heft to it. Nothing moves when hammering into the keys. ;)

I kind of don't care. I feel like it is not as comfortable but I get easier to the upper pinky key. No idea why.