Comment # 1 on bug 1177477 from Benjamin Greiner

Current packages in Tumbleweed:

python38-base provides /usr/bin/python3
python36-base does not provide /usr/bin/python3

This has been the case since the introduction of python38 at the end of July.

I do not understand how you could end up with your situation in the current
snapshot.

Just reinstall python38-base?