Hey ayocado, I have some experience with self-managed/self-hosted base maps. There are some modern tools that make the setup pretty easy (e.g. Protomaps, MapLibre) and you can still use a minimalist style similar to the CARTO one you have now.

If you're interested in switching over, feel free to shoot me an email and I can try to help!

Here are some demos [1][2] I've made without using any third-party map services. All open source! [3]

[1] https://wcedmisten.fyi/project/north-america-hospital-distan...

[2] https://wcedmisten.github.io/nextjs-protomap-demo/isochrone

[3] https://github.com/wcedmisten/nextjs-protomap-demo