I have proposed MapLibre as a new home, unaffiliated with any existing project, but at the same time inviting maintainers from everywhere, including OpenMapTiles (I'm a big contributor there), as well as other entities. So far a lot of positive response on twitter, hopefully it will pick up. See original post at https://twitter.com/nyuriks/status/1336493514646052864 (includes a nice reply from MapBox CEO)