Impossible to mount an Unraid NFS share on a remote Debian machine

I have a problem that I've been trying to resolve for several days now. I've tried everything I could, and I am failing spectacularly.

There is an Unraid NFS share I want to access from a different machine running Debian 12 minimal (fresh install).

Share name: MEDIA

Export: Yes

Security: Public

On the Debian machine, I installed nfs-common:

sudo apt install nfs-common -y

I then created a mount as follows:

sudo mkdir -p /mnt/UNRAID_MEDIA

Then, on the same machine I edited the /etc/fstab:

sudo nano /etc/fstab

and I added either the following line:

10.13.88.6:/mnt/user/MEDIA /mnt/UNRAID_MEDIA nfs defaults,ro,_netdev,bg,nofail,timeo=100,retry=10,anonuid=1000,anongid=1000 0 0

or the following line:

10.13.88.6:/mnt/user/MEDIA /mnt/UNRAID_MEDIA nfs defaults,ro,_netdev,bg,nofail,timeo=100,retry=10,useruid=1000,useruid=1000 0 0

After either of the two, when I type:

sudo mount -a

and I get the response "mount.nfs: an incorrect mount option was specified"

Also, the mount doesn't appear when I check with df -h , which makes sense as the mount failed.

I also tried this solution but again no result.

Then I tried changing the /etc/fstab line (idea taken from here) to:

10.13.88.6:/mnt/user/MEDIA /mnt/UNRAID_MEDIA nfs defaults,timeo=900,retrans=5,_netdev 0 0 

This worked. When I typed:

sudo mount -a

I could see the mount with df -h

But after I rebooted the Debian machine, the mount again was not there!

All commands on the Debian machine are typed with a user that has sudo proviledges.

Can someone help with what I am doing wrong? Is this an issue with Debian, or with Unraid?