If you are current on Solus updates, you should be running Gnome 3.38. Check your "installed" software in the Software Center, and "Settings" > "About". One my computer, installed software gnome-session is shown as 3.38 and everything else gnome seems to be on that version, as well, and "Settings" > "About" returns the shell at 3.38. If you are showing 3.34, try running the full sudo eopkg up. If yours is showing 3.38, I suppose its possible that gnome runtime for Flatpak is out of sync somehow, but that's beyond my skill set. I wonder if the Flarpack package might be out of date.
