Still the same error on edge
snap run --shell firefox -c "xdg-open apt://flameshot"
user-open error: Supplied URL scheme "apt" is not allowed
snap 2.45+git607.gda0d2c2
snapd 2.45+git607.gda0d2c2
series 16
ubuntu 20.04
kernel 5.4.0-32-generic