If I check the “Set as default” box next to these speakers in pavucontrol, the speakers work, and sometimes I can even test them, but the checkbox in the quick settings never appears, and switching to headphones results in me being unable to turn on the speakers again. I also tried to change profile in configuration tab from analog stereo duplex to analog stereo output. doesn’t work (no check icon on the screenshot, but my speakers work in that moment)
If you run alsamixer in the terminal and pres F6 and select HDA Intel/Realtek option, not HDMI.
In pavucontrol set Analog Stereo Duplex or Analog Stereo Output.
I am completely guessing but I would play around and see what works, back up anything important first although in my experience this is pretty safe, just remember the defaults
There is a nasty bug in gnome right now with sound.
For now, see if you can downgrade gnome-control-center from 49.4 back to 49.1.. the quick sound settings will still be broke, but at least you can go to settings > Sound and switch properly.