Minecraft doesn't show up in the volume mixer - no sound?

I recently built a new PC. Well, so far everything is going very well. Until I install Minecraft this morning: nothing noticeable at first, only the sound is missing. So I press F3+ T to reload the files, and look in Minecraft's sound settings to see if I have the overall volume at 0%. Nope. 100% - and the right playback device is also selected.
What seems very suspicious to me is that Minecraft is not displayed in the volume mixer.

Here is a list of everything I have tried besides the one described above:

PC restarted
Minecraft reinstalled
.minecraft folder deleted and recreated by restarting Minecraft

Could really use help, thank you in advance for your certainly many good answers.

I don't know if I'm just too incompetent to delete this question here, but in any case, the problem has now been solved:

I forgot to install the driver for my audio interface: /

So better ask Communty, thanks for nothing.