I could not find a digital that was internally powered (most thermostats are set up for 24 volts) for a reasonable (<$50) price....
I could not find a digital that had an "off" setting to insure the furnace would not fire up while unattended......
Most of the digitals I looked at appeared to be set up for a "microamp" 24 volt and minimal draw (18 gauage wire) contact requirement. I have not measured the 12 volt
amperage draw across the thermostat contact on the Suburban furnace, but I did not want to take a chance and fry something by installing an under-rated thermostat.
I actually wanted a digital unit, I like looking at something and having it TELL me in great big numbers what the settings are, rather than having to interpolate between tiny numbers on a scale. I would still probably replace the non-digital with a digital if I could find one meeting the above requirements. I should clarify, the thermostat I installed is electrical, rather than a straight mechanical, it just doesn't have the digital readouts.
One of the downsides of the electrical thermostats, the contacts close in the case of an internal battery failure. Not a good thing in a normally unattended RV.