There's zero chance that would be a direct attack by AFU. It's _possible_ it was some sort of sabotage operation (if so, it's much more likely to be Russians who oppose the war), but it's also a wooden barracks building... structure fires are a thing that happen for a whole range of reasons.

The chatter seems to be it was a conscript base. Either the conscripts didn’t want to go, or what also happens is that bases get understaffed for X amount of people while still getting the money for those “missing” soldiers. Getting rid of evidence then becomes an option.

A lot of the Russian conscripts seem to be minorities from more rural areas, and Russian military lifestyle is very subpar and is likely a downgrade for those conscripts from their home.

So yeah, the conscripts getting upset and burning down a base is very believable.