DnD 5e - any module
You know what, why not? How do you feel about a 1 on 1 game of Out of the Abyss?
I'm pretty partial to good roleplay and high-risk combat, and solo seems like a fun way to do that; don't worry though, I have several ideas for helping give your character the boost they need to actually manage to survive in the Underdark, including but not limited to some Bioware-style custom party members and maybe even a simple Deus Ex Machina system.
As for me, D&D 5e is pretty much the first TTRPG I ever played, and I am intimately familiar with all of its rules. I enjoy making clear and detailed posts, and I've been told that I tend to focus on characters and story more than anything else.
What do you think? Interested? We can hash out the exact details in the game forum if this is the kind of thing you're looking for.