By stock you mean xiaomi camera? If yes, you can install ANX Camera until version 139. And then install Dyneteve 48MPFix to be able to take 48MP photos (which is working now, by the way). I think I never installed GCam before GApps, so I'm not sure if it will run without them.
Can you tell me your exact steps please?, and additional info like, which rom you had before, and if you flash anything with fastboot and what with twrp, also, which twrp you used, and about vbmeta, you used it after, when you got stuck at fastboot as well?, sorry for so much questions but I really want to get rid of miui.
If you have any additional info/advice, I would really appreciate it.