@freefrog Thx for answering. I allready switched to google free android since I needed to use my phone. I will try to reinstall Ubuntu on weekend and tell you if it worked.
There is a device specific subforum for your device, and some topic with identical issue than yours.
@antidroid thanks for looking into that. A rather odd design decision but happy to know that also means they likely used an earspeaker that should tolerate high volumes.