Just a note that if you end up buying a bicycle instead of a smart bike, and you truly have zero desire to ride road/gravel, I think it would make sense to buy a cheap used hardtail (or even a new hardtail) with similar geometry to your high end mtb. My trainer bike has very similar geometry to my outside bike, but is aluminum. If I’m going on cycling trips that require me to bag and ship the bike, I ship this one and worry a lot less about damage to my nice bikes.
While nice bikes are hard to find in stock, the lower end stuff is plentiful at our local shops who are getting regular deliveries again now.