Unable to boot from USB/SDD on ACER Nitro 5 AN-515-42 with Radeon RX560

a couple of days ago I bought a new ACER Nitro 5 with its own Linux (Linpus Lite) system. But wether this already setup Linux boots nor the USB device with Ubuntu 19.04 that I just made. The shipped system just boots into a bash like this:

root@blablabla#

With the bootable USB device it is a little bit different: Sometimes the screen just stays black with no signal of activity at all. The other times it shows a couple of watchdog errors like descriped in this Bug Report.

I tried to edit boot options like mentioned in the answers to the bug report, but this didn’t work for me. And I have to add that I have no plan what exactly happens with/without those boot options. I tried to add:

ivrs_ioapic[4]=00:14.0 ivrs_ioapic[5]=00:00.2

didn’t work

ro rcu_nocbs=0-7 ivrs_ioapic[4]=00:14.0 ivrs_ioapic[5]=00:00.2 quiet splash vt.handoff=1

didn’t work, too

I turn secure boot off already, and the virtualization options, too. But this also had no effect. I searched the web for two days now without finding a working solution. But I’ve seen posts of person who did manage to install Ubuntu on an ACER Nitro 5. Unfortunately they asked about different problems in this forum. see here

Any ideas or help?

Thanks for any response.

pup