Yep, typical, is a very unregulated 18VAC from a “Doorbell/Thermostat” transformer, less a whole lot of voltage drop from the wiring.
It all depends how they designed the power input, but given the amount of induced noise and spikes long wires can get, I would rather not bypass any protection built into the designed power input circuit.
My building will be primarily 12V DC powered, and I am trying to avoid power wasting voltage converters where I can.
If (as I suspect) it stars with a bridge rectifier followed by a filter and voltage regulator, it is likely to run well all the way down to about 8 VDC.
Right now it is all guessing, till I get one. (Or someone else has done the work)