Pocketbase [0] is a possibility. It offers a way to subscribe to collections, meaning the client will be notified if any of the records in that collection change. [1] Should be quite efficient too, the FAQ claims that 10k realtime connections on a small hetzner VPS is no problem [2]
Currently my preference as well. I like the auth part and admin UI. Combined with htmx it makes building reactive apps (without React) relatively easy.