Just went down a nice deep rabbit hole of all kinds of nice blogs. Thanks for posting!

Have you looked into notmuch?

I looked into building something like this but I think most people are scared off because the TOS prohibit doing that, so I didn’t investigate further :/

Cool project, I’ve been looking for something like this!

I made one! It’s a solitaire-like but with some new mechanics, and fairly polished and balanced at this point. You can find it on itch and on the play store. Here’s the source.