Lots of ideas have already been put up.
Not very durable. Keyboards take a pounding. On my keyboard quite a few keys no longer have anything on them but I mostly touch type so it doesn’t matter. I consider it a security feature. 
Engraved or injection molded is much better.
You can also buy vinyl printed stickers.
I think that one area that is painful with any remapping solution is early boot i.e. you can remap in your installed Linux but you still have to contend with changing BIOS settings and Live Boots etc. which you have to operate with a keyboard where keys don’t do what the keycap says.
There is a lot to be said for remapping in low level hardware so that the keyboard “just works”, without remapping at a myriad of higher levels.