I made a blog post about solo gaming, with a focus on adapting rules-light games like Cairn

I also try and give an overview of solo RPGS in general.

This is maybe rather obvious to people who would be in this community, but I also recently read The Ink That Bleeds, which is about solo journalling games, which is a very interesting perspective on them - it's cool to see how other people approach solo games, which I think are ultimately a very broad genre