After testing multiple IP smart doorbell / cameras I find this particular camera to be very solid. It is also one of few budget cameras that has a switched output for opening an electronic gate. Plus, you can pair RFID keychains to open and close the gate. I just installed my 2nd camera because the old one got damaged. The old one has been on our gate for 6 years, fully exposed to typical wet north-europe weather and it worked all the time. Back when I bought the first camera it came with the Yoosee app, which I now find crap compared to the new Tuya app. The only thing I haven't figured out is how to re-enable ONVIF. On the old APP there was a specific setting to enable ONVIF, but that feature does not exist in Tuya app.

Mine is giving the error "already linked to another user"

This is Michael. I'm saying this to help you out. If you want to sell this thing, you need to show some video, both day and night, of its capabilities. You need to describe its features, such as its viewing angles Etc. And I strongly recommend a redesign. This thing looks like it's from 1960.

Can I connect the ethernet cable without PoE and power it with the 12V DC adapter?