We purchased a class C brand new in 2019 and it did not include a spare. Like many here I would lean towards roadside assistance if I ever needed to replace on the road, but I travel many places with no cell service so I need to be independently prepared. Immediately after buying the new rig I purchased a new Ford wheel and an exact match Hankook tire which I had mounted up. My C has an enclosed spare tire compartment so I threw the new mounted spare in there and paid it no mind. I moved the jack and breaker bar from the old rig to new.
End of first year as an experiment I tried to mount the spare using tools I haul with me, just to make sure I could do it. I tried worse-case-scenario - an inner dual failure on the driver's side. I was able to install the spare fairly easily with no issues.
BUT I learned was that even though I ordered a Ford wheel supposedly identical to the OEM wheels installed on my rig, the new wheel does NOT clear the rear brakes on the inner dual. It rubs and makes noise when mounted (SO CLOSE.) I did not try on the front. So what I did was put the "spare" I purchased after buying the rig on the outer dual and put a factory wheel as the spare. Now I know the "spare" will work in any position. I would have not known of the brake clearance issue had I not tried to replace in the driveway. So that was very much worth my time.
I encourage everyone that carries a spare try to install it in their driveway using only tools they carry with them, if they intend to be able to install it themselves. It made me feel much better trying it myself and it was not any more difficult than any regular tire replacement as long as you have a long breaker bar and the correct 6pt socket. Just the fact it made me feel more confident made it worth it, and what I learned about the brake clearance was definitely best learned in your own driveway.