Test camera from temporary image/fastboot/recovery mode ABD

I have a OnePlus 6, running LineageOS 22.1 (Android 15). In December when I still was on LOS 21 (Android 14), out of nowhere my phone's camera & torch have stopped working. It just shows "Camera in use" message under the Torch button in the notification area, the LOS camera app just closes itself, or other apps display "can't open camera". I've revoked camera permissions to see if anything is using it, but no change. Initially after a few reboots the torch was working, but later on even that stopped working & after many reboots & upgrades I can't get that back to work either. LOS support said to flash back the original OxygenOS, but I don't want to do that, as it will log me out of loads of apps which don't survive TWRP/OrangeFox restore. So what I'm looking for is a way of confirming that the camera is physically broken, so to see I'd need to try to replace it (if possible, didn't look at it), or there's some software issue only (I don't want to open the phone if not necessary). Does anyone know a way to do that, eg. from a recovery/fastboot boot/ADB or anything else? Or is there a possibility to boot to OxygenOS without flashing it in? Thank you