User-Agent:       Mozilla/5.0 (X11; Linux x86_64; rv:92.0) Gecko/20100101
Firefox/92.0
Build Identifier: 

After updating Tumbleweed from 20210927 to 20210929 (and 20211001) GTK
applications like Firefox and Inkscape adopt an "old-looking" Adwaita theme,
with non antialiased fonts and Adwait cursor. For instance, on Firefox, moving
the mouse in and out the window makes the mouse cursor change to (what I
believe is) Adwaita's default one, hence not following the default Breeze dark
cursor.

Reproducible: Always

Steps to Reproduce:
1. Update from 20210927 to 20210929 (which I believe is the snapshot causing
the issue)
2. Open Inkscape, the splashscreen has non-antialiased fonts, the cursor when
inside the window does not respect system's default one (Breeze Dark in my
case)
3. Open Firefox, a similar behavior happens: the cursor, when inside the
window, changes from Breeze to Adwaita's one. It reverts back to the default
one when placing the cursor outside the window.
Actual Results:  
GTK applications stop following the GTK theme set by the user and revert back
to Adwaita, with non-antialised fonts and general old looking theme. Setting
back a custom GTK theme normally used by the user has no effect, even after
logouts or reboots.

Expected Results:  
Both GTK applications shall resort to the GTK theme adopted by the user, not
Adwaita's one.