snap install authy --beta
Setup snap "snapd" (10707) security profiles \
2021-02-03T20:20:50+08:00 INFO Waiting for automatic snapd restart...
authy (beta) 1.8.3 from Twilio Authy installed
[sf@vostro ~]$ authy
WARNING: cgroup v2 is not fully supported yet, proceeding with partial confinement
Sorry, home directories outside of /home are not currently supported.
See https://forum.snapcraft.io/t/11209 for details.
Hm. The forum post linked in the error description suggests to bind-mount your home directory to /home/username.
In your case that would mean rm /home, mkdir /home and mount --bind /var/home/username /home/username. But I’m not sure how Silverblue behaves when /home is not a symlink, so be careful or don’t do it at all.