Override environment variable so snap runs on wayland

Have a nice new hdpi monitor, but it only looks good if I use scaling on Wayland.

I’d like to test if the beta versions of Thunderbird have less bugs than the current version in Ubuntu.

The snap betaversion of Thunderbird starts with the wayland environment variable disabled. At least that what’s I can see in snapcraft.yaml file. But I cannot edit and change that file. Is there a way I can try Thunderbird beta with wayland?