service centre has emailed back to me on the SD card issues on MM related to 3rd party apps and the response is pretty lackluster.
Long story short they said 3rd party apps "dont have permission" to write to SD card so I should just wait for every developer of every 3rd party app to properly support LG's MM.
The problem here is, it's not that the apps dont have 'Permission' to write, because clearly they can still create files on SD card, and clearly I can still grant an app SD write access through the storage access framework which is still there in MM.
The real problem is that these files, once created on the SD card, are completely unreadable on MTP or LG Bridge (they show up as 0kb files), worse still, this appears to be intermittent and random-- sometimes when i copy a large amount of photos to the SD card, a small percentage of them actually still are readable with no issue, while a large majority will still appear as 0kb when I view on the PC. This is a sign of something in the MM software not being properly ironed out.
Since LG has denied this being a real problem (because their email says app devs have to take effort to support LG's V20xxx software's mysterious SD card write-permission implementation), MM on the G4 is to me hereby a permanent no-go for me (doesnt help that the MM battery life is still garbage)
I actually have to visit the service centre again to try and replace my camera element cos the lens coating has worn, if they tell me they're going to wipe phone, hopefully I can request a flash to v10 and not v20