i used this this test with Brave, Thorium and LibreWolf.. ..Brave and Thorium passed, LibreWolf failed..
Discussion
The only trick is that Thorium UI is rendering at 2x. It doesn't seem to follow global env variables for GDK_SCALE or Wayland scaling. Assume you're running on X11?
example i3 keybinding to fix this: (adding GDK_SCALE=1)
bindsym $mod+b exec --no-startup-id GDK_SCALE=1 thorium-browser
example .desktop file to fix this: (adding GDK_SCALE=1)