Well, this may be a daunting place to start for someone new to solo rpgs, but someone just posted about Lands of Eem in the “What’s On Your Table” thread. Everything I could find suggests it would work well with just a GM emulation deck (like what’s mentioned in the post). But as a former D&D player, maybe it wouldn’t be too much? It’s definitely a less complicated TTRPG by comparison.
Anyway, regardless of whether or not that’s for you, welcome to the forum! Plenty of solo boardgame/rpg recommendations to find in here.