Limitation seems to concern paid features only for the time being (I only realized this when I couldn't sponsor a project yesterday).

As long as you are limited, you cannot update your billing address.

The only way to lift the restrictions is the appeals form*, which requires submitting a non-Russian photo ID. Apparently, regardless of where you reside, a Russian user who paid Github from Russia or with a Russian billing address at least once must obtain another citizenship (probably not a problem for the wealthy ones?) to keep using their existing Github account fully.

* https://docs.github.com/en/site-policy/other-site-policies/g...