Yes, and no - be wary!
The TVs that have a transformer to convert 240V mains to a 12V DC supply have a REGULATED transformer and they expect a consistant and specific 12V supply. A motorhome leisure
battery system may be called a "12V" system and sockets called "12V sockets" but the output is anything but 12V!
If you just bypass the transformer and plug a TV that wants 12V into a motorhome, you run the risk of damaging it - usually beyond economic repair - as soon as you put a
battery charger on and the "12V" voltage goes to 14V and beyond.
lots of people will have had no problems of course, and that's great for them - but maybe you will be one of the ones who blew up their TV (or lights, or other domestic products designed to work on 12V precisely, and not a range of voltage from 11V - 14.5V)