@Butterfly60
Interesting question and I could be wrong but I don't believe you'll be able to use a non roku device/camera on the Roku Smart Home App.
Two other thoughts came to mind that I thought might be worth sharing. A lot of the cheap cams you can find out there only work with P2P (Point-to-Point). Basically you scan a QR code or put in an ID number and it connects via your Wi-Fi to an offshore server. I'd be careful with this but that's just me.
I only use Roku branded cameras, lights, and security products and have the Roku Smart home app and have found it great. The one thing I can think of is i've seen an App on Roku TV called IP Camera Viewer Pro. There's a basic and a paid Pro version. I'm not very familiar with with it but if you typed IP Camera Viewer into the search bar on your Roku TV it should pop up and you can take a look. I can't vouch for it though since I've never used it or know anyone how has.
One last thing I'm not sure if this is what you're looking for but Roku has a handful of different camera options on their website and they go on sale from time to time too. I'd take a look there. Maybe you'd find something that fits your needs and budget.
Best of luck
