I've been working on a project along these lines recently. I've called it Dogsheep - the basic idea is to have scripts that export all manner of my personal data (from Google, Apple HealthKit, Twitter, LinkedIn etc) into SQLite database files, then use my Datasette web app to browse them and run interesting queries.
More about that here: https://dogsheep.github.io/
The tools I've built so far are under https://github.com/dogsheep
I think that Perkeep https://perkeep.org/ is also worth mentioning here. One of their latest tools is the one for exporting Google Photos: https://github.com/perkeep/gphotos-cdp