Unfortunately your debug log starts after the interesting part:
2021-03-28 13:18:24.577 T:1048 INFO <general>: VDPAU::CreateContext - creating decoder context[...]
2021-03-28 13:18:56.979 T:1048 INFO <general>: Enabled debug logging due to GUI setting. Level 2.
radeon.cik_support=0 amdgpu.cik_support=1 brings back the VAAPI and simply works.
Which LE version did you use before yesterday?
There was both a Mesa and a kernel update yesterday. With the amdgpu driver still working and having used a recent LE version you can start to revert the kernel update first.
A general question: Does AMD_GPU work with VDPAU-Decoder at all?
You have to configure it. Create:
and restart kodi.