I don’t think the coma is currently detectable with “small”, i.e. sub metre class, telescopes but the image from the ATEL reference above looks reasonably convincing.
It is interesting that 2I/Borisov was definitely cometary and it looks like 3I/ATLAS is as well. 1I/Oumuamua was not but it did have anomalous nongravs which implies it must have been comet-like. This paper suggests that the thrust in that case was from sublimation of molecular Hydrogen: