Piping gravity fed condensate line down interior wall into crawlspace then through rim joist to outside

Could you do it sure , but you will need a pump to go horizontal can’t just dump under the house unless you want other problems and it will be found on an inspection if you want to sell.

If you don’t mind a 45 or steeper slope to an outside wall that could be done also and would be a better option than under the house in my opinion.

Under the house you are really taking a chance of something as simple as a spider building a nest in the drain line. Any obstructions tend to cause the system to back up.

Regarding backups It’s not just 1 brand several brands I have installed and very high end units I have been called to fix, I see no water in the down pipe but a slight plug in the pipe opening and the water is overflowing inside The machine(s) have been level but the tray is over filled and pouring out (ok more like a dribble, Or the safety shut the machine down) the home owner(s) always want to know why/ not happy hot house.

To date I have seen several spiders , grass clippings and earwigs being the cause and 2 or 3 that the hose curled up and the water made a trap once straightened the problem was gone hence my forcing the drain straight below the Chanel covering.

I am not sure if it is the ridges in the pipe or what make them back up so easily. I have seen it quite often to the point I cut the lines several inches above the ground and tape a rod to the pipe so it stays straight and cannot curl.

In the training classes I have asked and so far no one has given a satisfactory answer other than the ribs.