Nextcloud - unable to add local storage / external storage App

Hello,
I'm unable to add local storage with the external storage app (red icone with exclamation mark)
but I have no issue with SMB/CIFS shares connected to a Synology for instance

In my case, the folder I want to connect is "F3"
The local path of the folder on the OMV is "/sharedfolder/F1/F2/F3"
Folder "F1" is the shared folder

F3 is reacheable from my computer with SMB/CIFS

I read in a previous post that in the "configuration" field of the external storage App, we have to enter the container path
->I don't understand this part

I tried enter "/data" (as "/data" is my container path), and it worked.
So I guess I have permisson issue or something else ?

I also tried to change permission on the "F1" folder but it's still not OK
https://docs.nextcloud.com/ser…ternal_storage/local.html

Can someone help ?
Thank you

I guess it is resolved now.
I don't know if it's the good way (I'm a noob), but it worked

1) Thanks to @MrC, I created a new container path, mapped with the desirated sharedfolder I want to connect
2) I added a "local" external storage, with the container path entered in the configuration field
3) In order to write into the mounted storage, I ran a chown -R 911:911 /Path/to/folder

If somebody have a better way to achieve, please share