In another thread I read that amd-gpu-firmware and xorg-x11-drv-amdgpu might be important. Additionally the output from dmesg could be useful.
liveuser@localhost-live:~1$ dmesg | grep amdgpu
liveuser@localhost-live:~$ dmesg | grep amd
[ 0.650055] amd_uncore: 4 amd_df counters detected
[ 0.650060] amd_uncore: 6 amd_l3 counters detected
[ 0.650290] perf/amd_iommu: Detected AMD IOMMU #0 (2 banks, 4 counters/bank).
[ 5.654704] amd_pstate: driver load is disabled, boot with specific mode to enable this
[ 19.842111] kvm_amd: SVM disabled (by BIOS) in MSR_VM_CR on CPU 0
liveuser@localhost-live:~$ dmesg | grep gpu
liveuser@localhost-live:~1$ dmesg | grep radeon
liveuser@localhost-live:~1$ dmesg | grep graphics
Both amd-gpu-firmware and xorg-x11-drv-amdgpu are already installed
modprobe --showconfig | grep blacklist does not contain amdgpu, but radeonfb. Is that relevant?
Another recommendation in that thread was to look at GRUB_CMDLINE_LINUX in /etc/default/grub: The “default”-directory does not contain grub (probably because I am only on the live system and haven’t installed it yet?)