Actually, you don't even need that! The US Mac layout with level3_shift is very practical and supported with standard xorg (never tried wayland): the win keys become the level3 shift, so you can type special characters with both hands. win+c -> รง, etc. You also retain both alts as regular alts. That's configurable, so if your keyboard lacks a righ win and is replaced with the menu key, you can use that as lvl3 shift.
The advantage is you get to keep both alt keys as alts. The downside is that you lose the Windows key, but I remap that to caps-lock.
The advantage is you get to keep both alt keys as alts. The downside is that you lose the Windows key, but I remap that to caps-lock.