@Phillip_Spellman I actually ended up solving this in this thread here: Permissions issues on local external folders
I also ended up opening up an issue on the github page to try and clarify what exactly the permissions issues was with externally mounted local folders. https://github.com/nextcloud/server/issues/10650
The issue was indeed permissions though it was multifold and somewhat complicated due to my particular setup.
While I have already fixed this issue using bindfs and by adding david to www-data and www-data to david groups, and changing the umask, I think this might be more easily fixed by changing the default writer permissions configuration of my nginx server.
Though that would still cause problems for folders and files created in Nautilus etc because their default umask would still be too restricted for www-data which means that the stuff I did fiddling with the dbus files would still need to be done in order for this to all work seamlessly.
And as noted in the Github issue there are still risks in setting up and using NextCloud this way, but so far I haven’t had any trouble.