I just did what looks like a successful upgrade from Debian 11 (Bullseye) to 12 (Bookworm) https://www.debian.org/releases/bookworm/amd64/release-notes/ch-upgrading.en.html
I just upgraded my Fedora Silverblue 37 VM to 38, and it was very smooth
These are the Flatpak apps I'm running:
AbiWord
Boxy SVG
PDF Arranger
Foliate
Flatseal
Chrome
Extension Manager
Bottles
Texmaker
GIMP
GNOME Boxes
Deja Dup
(GNOME) Web
Rhythmbox
Inkscape
LibreOffice
Firefox
RaspberryPi Imager
Zoom