How to make Ctrl+alt 3rd level selector (Alt Gr) on Linux using Wayland?

How can I make Ctrl+Alt be the third level selector, similar to Alt Gr, in Wayland?

All solutions found on the internet are very specific to Xorg and any key remapping software such as AutoKey or xbindkeys will not work in Wayland

This is very important in many European keyboard layouts as e.g. Alt Gr + (7-9) is very cumbersome to type otherwise