Just finished going through every location where the scroll merchants are supposed to be and they are not there. The potion merchants are showing at their locations, however.

I only have steam deck. I don't have a pc. Do they have IDs? Making them spawn via console seems easier.

If the mods you're using modify navmesh or landscape in anyway, NPCs from other mods will either fail to respawn or stuck underground.
You can try to
1. make a patch yourself, but you'll need third party tools such as TESV Edit
2.Load my mod AFTER other mods (my mod only add simple NPCs without touching anything else, so load order won't mess up anything)

I use Whiterun + Forecourt, the learning stone, dragonsreach imperial overhaul, your potion merchant mod, and this mod.

Is it possible that you modded Whiterun? I tested in my game and the merchant was there

Some seem missing. Looked up and down for the one at Whiterun between the back of the Bannered Mare and the barracks and he is nowhere to be found. :(