I haven’t used them myself, but keyshorts.com has custom keyboard stickers with many options. Background color, text color, custom size & shape to fit keys exactly, multilingual sets. That’s what I’d go for. They do list Framework as a brand they support for custom shaped stickers.
Custom Keyboard Stickers Builder | Keyshorts
This is also a way to get RGB in other languages. Get a clear keyboard and buy exactly sized stickers in your language.
Note that all the options actually use QMK firmware.
Definitely, works in Linux. I’m on Linux and use QMK.