I’ve done some more digging, looking at the upstream unofficial Lineage builds
in the 17.1 / Q build and and the 18.1 / R Rom the developer suggests installing a different app to get over limitations in the default LOS Camera App. He suggests OpenCamera, which I believe is the upstream from which /e/'s app is forked
Both shipped camera app *) and OpenCamera are fully working and shows the viewfinder/preview.
Unfortunately this leads to the maximum of 8,3 MP for the main camera.
If you prefer 23 MP, you should remove OpenCamera and install this version of this app instead. Go to the settings and choose the option “Open Legacy for Camera1 API”. With that you get 23 MP back, but no viewfinder/preview.
Maybe worth trying the linked version OpenCamera, though you may need to disable /e/'s Camera app. Alternatively, try some other camera apps from F-Droid or Aurora Store.
Sorry I can’t try any of these things out, but I no longer have /e/ working on any of my devices, and I can;t tell the difference between a good camera app and a bad one
Other commentators have suggested trying one of the Open Gcams which can leverage the Sony proprietary blobs that are included in the /e/ build but are not fully open to OpenCamera.
I can see how this might solve similar milder issues with my Samsung. There are hundreds to chose from; I never found the one which would resolve every detail.