I'm actually using Github issues as a low-volume/high-latency DB for a project right now. I use a Netlify function to do extremely simple auth and then open an issue on Github, which triggers a CI action, which appends to a .jsonl file in the repo (different branch), which triggers a Netlify build, which then serves the new jsonl file. (If the repo were public, this wouldn't even have to trigger a rebuild of the website, it could just get the .jsonl from Github directly).
It's totally hack-a-licious but it also totally works for my N<10 users.