ARW expressed precisely :
What is the norm on them these days?

A mixture of 12V from a leisure battery and 230V for when there is a 230V
hook up. Inverters?

Pretty much, plus a few sockets, 3 way fridge, 2 way heating systems,
antenna amps, radio, possibly a remote control mover, possibly an
alarm, possibly a tracking device. All fed via an RCD small consumer
unit, with a 13.8v switch mode charger/ PSU, able to power all the 12v
in the absence of a battery.