Interesting to see continued activity in this thread!
It’s worth noting that DirectFB is now very firmly in the “dead projects” category after a few false deaths! The main author, Denis Kropp has now moved onto other projects.
It’s probably still worth keeping around for existing codebases, but I don’t think there will be any new developments in this space.
One of the main backers, Broadcom, are no longer supporting it much.
As to whether /dev/fb support would help, the answer is maybe - if what you’re doing is single window stuff, perhaps it could. DirectFB has a multiapp mode though which wouldn’t be helped by this.
SDL2 is actually potentially useful for migration since it support both DirectFB and GL platforms.