Problem with Ubuntu?

I have the problem that when I play Minecraft on this laptop and press the volume key on the computer, Minecraft automatically throws me to Firefox (at least if I have it open). And then much does not work anymore: eg the touch bar the red x and so on. Would be happy about help.

For this very bug I could use the Linux version of Minecraft ******

Yes, if you are in full screen, Minecraft will throw you out when changing the volume. The only thing that helps is to launch Minecraft in windowed mode (& maximize the window). Or before (& after) change the volume press F11.