You still need to change the 5GHz radio to "Off." To do so, from the image you provided as reference, tap on the "grayed-out" 132 channel. You should get a drop-down with a number of channel selections. Tap on "Off."
I also managed to locate the setup instructions for a number of Eufy cameras. It claims that even with wireless routers that provided simultaneous 2.4 & 5GHz bands, that the camera is able to connect properly to just the 2.4GHz one. Doesn't appear to be the case for you here. Sorry, I don't use Eufy cameras, I use Ubiquiti UniFi ones, so I'm not sure I can be of anymore assistance with this matter. Good luck!