>>4091062i use opencamera (f-droid), it has the option to record RAWs if your phone's camera driver allows it, i don't know how common it is, but i've done it one two phones and both have supported it
after installing it, you have to go into its settings and set the camera API to "camera2", it's not the default, camera2 api is the one which supports things like raw saving, manual focus/exposure/iso, exposure locking, etc
it's also just generally a rather advanced camera app, featuring things like a live histogram, focus peaking, zebra stripes, etc
