I recently discovered https://www.cozodb.org/ which also vector search built-in. I just started some experiments with it but so far I'm quite impressed. It's not in active development atm but it seems already well rounded for what it is so depending on the use-case it does not matter or may even be an advantage. Also with today's coding agent it shouldn't be too hard to scratch your own itch if needed.
cozodb is quite impressive and I've wondered about the funding sources etc on it, if any. I've watched it for some years and the developer seems to have made a real passion project out of it but you're right it seems development has tapered off.