I have noticed that sometimes a Gramps database will not show up after the update to 5.2. If this happens:
close Gramps
(if you use the flatpak) make sure your database file (.gramps or .gpkg) and all media files are within either Documents, Downloads, or Pictures. (Starting with the 5.2 flatpak, Gramps is restricted to only those three directories for improved security.)
open your file browser and find your .gramps or .gpkg file that you want to open
right click on the file you want to open
select “Open with Gramps”
wait a couple minutes for the database to update to the 5.2 version.
If anyone needs to go back to the Gramps 5.1.6 flatpak, there is an archived flatpak for temporary use at the gramps-project github. Reasons to go back might include making a backup of an old database or converting a BSDDB3 database to the current SQLite database used by Gramps.
Just be aware:
The 5.1.6 flatpak uses flathub runtimes that probably won’t be available in a couple years because Gnome stops maintaining old runtimes after a while.
(Edit to remove warning about locales. The archived flatpak uses the system locale now as of 26 Feb 2024)