Android - How to change photo storage path for LineageOS 16's Camera app?
As of right now it is not possible for you to change the path. Android Pie does not allow apps to write/read SD Card public area and only allows apps to access the application private area. That being said inside of Lineage OS Gitlab Repository there are several discussions to fix this problem. Maybe it will be fixed in the future with an update of Lineage or the integrated camera App.
Know this was a couple of months ago, and you may have found the solution. But I came across this very problem and the above info is mostly correct, you need Open Camera;
I don't know why Snap can't do it but in Open Camera > Settings > More Camera Controls > toggle on Use Storage Access Framework then navigate to /storage/Micro SD card id/DCIM/Camera & Save Location.
That works on S5 G900M LineageOS 16.0 klte build 2019-04-02 + Open GApps Pico + LineageOS Addonsu.
Works on my Samsung Galaxy Note 4 running LineageOS 16.0-20191129-UNOFFICIAL-trlte