Something tells me Chromium is returning soon to Debian Testing/Bullseye https://tracker.debian.org/pkg/chromium
Debian Bullseye ships with Python 3 by default and not Python 2. Also, you'll need to use the python3 command because the /usr/bin/python symlink is deprecated, though you can restore it with the python-is-python3 package. Python2 is still available. https://wiki.debian.org/Python
In Debian Bullseye, GNOME Software handles updates for Flatpak applications. This was broken in Buster (or at least was in my installation). It's one of many nice upgrades in Debian's current Testing branch.