Believe it or not, this is actually an improvement. It tells you that the server is now reading the SC3plugins .so files, where it wasn’t before.
The details of the error are important: “version ‘GLIBC_2.33’ not found” – this points to a system library problem, not strictly a SuperCollider problem.
TBH I’m out of my depth when it comes to system libraries in NixOS, because I’ve never used it. In Ubuntu, a similar problem could likely be solved by installing a package.
I do find a thread on the NixOS forum: `GLIBC_2.33` not found, although it is installed - Help - NixOS Discourse
hjh