As far as I know, there are no "Free Map Tiling provider"-s. This project aims to be exactly one. You can use it with Leaflet using the https://github.com/maplibre/maplibre-gl-leaflet plugin.

I asked the question as a top level comment but also duplicating here. Isn't Apache Baremaps a "free map tiling provider"? Or do I misunderstand what a tiling provider is?

https://baremaps.apache.org/

They are providing the building blocks for making a self-hosted vector tiles server, they don't actually host the tiles.

Interesting thanks, I've used map tilers in the past without paying, maybe I just never came up against any rate limiting