Have the same issue. In fact not able to use the camera from any app like WhatsApp or Google Duo
I did install the OB20 n now on the OB21 for my OnePlus 5t through the twrp recovery after deleting the compatibility zip. All worked well or rather...
Try the ones that are sold by Gadgetshieldz. They are quite good and ship globally too.
Might as well just the 4:3...better res for printing pics.... I know that's not really a use case now a days... But just in case;)
I reckon the sandstone one. Bring back memories of the original one plus
Which phone are you coming from? One plus generally has bundles more than usual..... Or else root your phone and enjoy