So, first issue, popovers (eg., drop-down menus, app menus, etc.) don’t work on GTK 4 apps (like System Settings in GNOME) on touchscreen devices.
Three-year old bug here: https://gitlab.gnome.org/GNOME/mutter/-/issues/1523
I guess that means tablets are not currently supported under GNOME.
Will see if KDE Plasma works on touchscreen Linux tablets.
*sigh!*
Update: Issue fixed in GNOME. Works in latest Fedora (tested w. Silverblue). Ubuntu doesn’t. HT @sonny