Craig Campbell and NerdBurger games have had a string of acclaimed Kickstarter successes. The latest campaign, Secrets of the Vibrant Isle, is a solo tabletop RPG.
I think downloading a copy of Starlogs is a no-brainer. Even if you don't imagine you'll be soloing any time in the future, you can use Starlogs for GM or even PC background inspiration.
A Good Death is a solo RPG and journal game from Trent Seltzer. It's a Name Your Own Price download from Itch.io. I paid $2, and I'll get way more value from it than that.
The system procedurally generates entire dungeons and other fantasy landscapes suitable for flatscreen TVs or VTTS. They don't get into the details, but it is also possible to have physical tiles created and sent to you.
Splintered Realms Publishing released this week Super Solo: A Solitaire Framework for Superhero Gaming.
Your wanderer is a former Samurai who is now an outcast, having lost their honour. What exactly happened to put you in this state is up to the dice and your imagination.
A non-D&D game looks like it'll have some sort of presence at Dungeon Con Online as Graycastle Press has released Journey - Dungeon Con 2021 bundle.
Designed for solo play, "So You Want The Tall Vampire Lady to Catch You" is relatively unique in that the win condition is the loose condition, and the game takes a healthy attitude to both. Whatever floats your boat.
You're trying to build your dungeon, stock it and defend it. You're trying to follow orders from the master, and those annoying heroes keep invading.
In Journey, you are a traveller exploring worlds of your own creation. The game's designer, Luke Miller, suggests it's a good tool for writers, designers, game masters and the uncommonly curious.