Linux has changed.
- /etc/default was the old method until systemd became standard in 2020.
- Systemd allows customization in /etc/systemd/system/servicename.service.d/override.conf
I’ve been using Unix since the 80’s and started with Linux when it came out in 1998.
Plex runs as its own non-privileged user.
Giving PMS free reign on a machine isn’t always the wisest thing.
There are many users who want PMS constrained so that’s why it it’s default is constrained.
You can customize the config (in systemd) to be as unconstrained as you wish as well as move PMS’s AppSuppDir to wherever you want.
(That’s how I set it up)
As for Mint, I am relaying to you what our experiences are.
If Mint were a vetted OS, it would be listed.
For reference: There is a Linux Tips section here in the forum to show you the most common tasks.