I think n8n supports sqlite or postgresql, or do you mean am extra database to do other stuff?

Ok, it wasn't clear because supabase it's not even self-hosted. I checked out baserow and grist and you can connect it to an external postgresql db so it should be valid for your use case. I personally used omnidb but it looks abandoned

I’ve tried a few of these, and I’ve never found one that doesn’t feel like I’m inviting a sales rep to live on my home server. They’re technically open source, but it’s obvious their primary purpose in this form is to upsell you. I understand it, but it’s just not what I want so I’ve ended up getting rid of each one after tinkering with them for a while.

I guess the same could be said for n8n, but I find it more tolerable. I have set up a Valkey instance though and use it for persistent storage through n8n’s Redis support. That works well enough for my fairly limited use case.