2 points
I just changed one of the existing layouts. Very easy in any text editor, you just need to find the proper name or Unicode code for each function/character.
1 point
If you’re using xkb, try this guide. Of course, backup any system files before modifying them, and just to be sure, add a 2nd keyboard layout as backup and know how to switch between them to have a fallback if you corrupt the primary one.
There might be TUI or GUI tools too, probably way more convenient for a one-off change on a single PC.
