RTSP not working with Reolink IP cameras

First verify in the camera settings that RTSP is enabled (with new firmwares RTSP can be disabled by default)

Usually the Reolink cameras expose the following streams, e.g.:

main stream: rtsp://user:password@192.168.5.32/h264Preview_01_main
sub stream: rtsp://user:password@192.168.5.32/h264Preview_01_sub

But some Reolink cameras (e.g. 4K) expose the following main and secondary streams instead, e.g.:

main stream: rtsp://user:password@192.168.5.32/
sub stream: rtsp://user:password@192.168.5.32/h264Preview_01_sub

Note: to connect by ONVIF, verify also that ONVIF is enabled in the camera settings.
The default ONVIF port is 8000, e.g.:
onvif://user:password@192.168.5.32:8000