Reolink and Lorex both make doorbells that expose rtsp streams. They have apps and such but these aren’t necessary, and at least reolink doesn’t require a subscription even with the app (not sure about lorex). The reolink comes in Poe and WiFi version, not sure about lorex. I have reolink Poe cameras (including doorbell) and they work great, everything is local only and aside from the initial config they do not require internet access. I have them on an isolated vlan that has no internet access and they work fine. They make WiFi versions too but in my experience Poe is substantially more reliable if you have the ability to run ethernet

There are many other options too, there’s like a billion doorbell cameras, just research bc almost (if not all) “cloud” cameras can view the footage on their servers. The only thing I’ve seen is encrypted in transit, they all are not encrypted on their servers. This means their employees, intruders, etc can view your cameras (and in the case of stuff like Amazon and Google actively view it to apply ML models as well as actively share with law enforcement with no need for a warrant). This applies to literally every “smart” camera I’ve seen that’s not local only, whether it’s a doorbell, baby monitor, dog treat dispenser, basic security camera, etc