Trail riding 100%. When I lived in San Jose I rode 100 miles a week and barely on the road. I’ve done a ton of century rides and charity rides and did that big 500mile tour in 2016 on the road. Cars are so gnarly on a bike.
This is where the gravel grinders are so good. Mine is a Pake CMute I got in 2009, it’s steel and will last forever. I’ve set it up a dozen different ways. I’ve raced it, rode MTB trails and done centuries on it and it keeps going. I’ll hang it up for months until the tires go flat and bust it out like it never hung for that long.
Highly recommend gravel grinders (not a CX bike, those are for racing). We used to kinda have to build them up mixing and matching road and MTB parts to get good gear ratios but now all the major bike companies make good ones out the box.
I rode a rigid single speed 29’er (no suspension MTB) for years, too. That was super fun. Even had it as a fixed gear mountain bike. Fixed gear on the trails was way too weird, but also awesome. Single speed MTB’ing involves a LOT of upper body and will keep the arms, chest and shoulders in great shape as opposed to just sitting and spinning on a road bike.
I juuuuust built up my Bridgestone as a 26” rigid single speed. I need to get it out on the trails but again, it’s time, maaaan. So little of it I have!