Urchich is an analyst at Aviation Week. Warning it is a long thread. This is the conclusion.
The MiG-29s in Libya are probably MiG-29C 9.13 models that Belarus did not upgrade (disagree with Scramble saying probably the BM upgraded type).
So the question is pilots. Belarusian mercs? Another friendly? Russian?
If Russian...Wagner group? Well, Wagner is not known to be in the fast jet game (yet) just helicopters as seen in their operations around Sub-Saharan Africa. This mystery remains to be confirmed.
About the MiG-29C 9.13, it has particularly bad range if not upgraded, and was weak in beyond visual range as well. Couple with less than elite pilots and if these are meant to square off against GNA/Turkish planes like the recent announcement of Turkey allegedly sending F-16s