Monnow; I just purchased, in December, my Ring Doorbell Pro and two Floodlight Cameras for a 2nd home. All were just installed at the beginning of January and all can be seen through Smartthings. I just recently purchased 4 Spotlight Cameras with Solar panels and they are waiting for me to install them. Hopefully they all can also be seen from within Smartthings.
I have to admit my 1st home has numerios ring cameras but all were purchsed in 2018/2019 and also can be seen in Smartthings.
I do remember that the Floodlight Cams that were installed in the 2nd home went through updates when then came online. Maybe that is the issue for yours.
Good luck.
Maybe the Moderator can give us an update on any intergration issues.