VersaTiles

VersaTiles, "a completely FLOSS stack for generating, distributing and using map tiles based on OpenStreetMap data, free of any commercial interests" looks like a promising contender to OpenMapTiles.

Both are interesting alternatives to commercial map services (for certain applications, YMMV) – and VersaTiles likely very similar in terms of setup – for self-hosting maps, which I have written more extensively about a few years ago: