I need to use Skype and MS Teams for work. So I have installed Skype from the repo at https://repo.skype.com/rpm/stable/skype-stable.repo, and MS Teams from the RPMs at https://packages.microsoft.com/yumrepos/ms-teams/. However, neither in Skype nor in Teams do I see any video or audio devices.

Skype complains that it can't find a microphone, video cannot be turned on, and the settings window does not show any microphones, cameras or speakers. Teams just doesn't show devices in the settings screen. There are no error messages when starting skypeforlinux from the command line, and no relevant messages in /var/log/messages either.

Video and audio devices are visible and work fine in other programs, such as Zoom.

I see the devices (here with one external, one internal webcam):
$ ls -l /dev/video*crw-rw----+ 1 root video 81, 0 16. Jun 12:47 /dev/video0
crw-rw----+ 1 root video 81, 1 16. Jun 12:47 /dev/video1
crw-rw----+ 1 root video 81, 2 15. Jun 10:48 /dev/video2
crw-rw----+ 1 root video 81, 3 15. Jun 10:48 /dev/video3
My user is in the video and audio groups:
users video audio 
I also tried the old camera trick for Skype:
LD_PRELOAD=/usr/lib64/libv4l/v4l1compat.so /usr/bin/skypeforlinux
But it doesn't help either (it seems to be for a different situation, where the camera is there and just doesn't work properly).

It didnt work initially, then I added my user to the video and audio groups yesterday, then after a reboot it worked for a while - now today it's gone again, but I can't remember doing anything about the configuration that would have changed it.

Any suggestions?