Deleting Files on Shared External Drive

I am running Nextcloud on my raspberry pi with an externally mounted ssd attached/mounted. I am able to view my files in my instance. I use Syncthing to backup files to my drive. Here is one of the created files:
-rw-r–r-- 1 pi pi 1009K Nov 22 13:27 IMG_20201122_132755.jpg
Syncthing is running as the user, pi.
When I go to delete this file in the browser/nextcloud, I receive this error: “Error deleting file IMG_20201122_132755.jpg”. It looks like Nextcloud is running as such, with the avahi user:
avahi 608 0.0 0.1 5900 3084 ? Ss Nov18 0:08 avahi-daemon: running [nextcloud.local]
What is the best way to approach this, to allow web interface users to modify files, like delete them?

Just wanted to follow up on this and see if anyone has any advice?