I know that ubuntu "masquerades" snap installations as having come via
apt. I don't see that on bullseye though.
I have installed "lxd" (which is not packaged as a .deb) via snapd.
root@piserver:~# dpkg-query --list lxd
dpkg-query: no packages found matching lxd
root@piserver:~# apt install lxd
Reading package lists... Done
Building dependency tree
Reading state information... Done
Package lxd is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source
E: Package 'lxd' has no installation candidate
root@piserver:~# snap list lxd
Name Version Rev Tracking Publisher Notes
lxd 4.0.4 18152 4.0/stable canonical✓ -
While you could clearly install e.g. spotify via snapd I don't see how
you could do this by accident.
--
Richard Huxton