Apple IOS 18 upgrade and iPhone access to NAS LS210D Series

[pgray]

I am having an issue with being able to store files on my NAS since the latest release of IOS 18 from Apple for their iPhones.  After speaking with Apple Tech Support they have told me that the disk format used on the drives for my NAS "XFS" is no longer being supported by the Apple IOS operating system.  They recommended that I use an Apple format APFS which will permit the writing of data to the drives. 
Looking into the format capabilities of the NAS Navigator 2 there is only one type of format available for the drives.  Access from my Macbook Pro does not seem to be affected by this update but I have lost the ability to write to the NAS from my phone.  I can read just fine, but I just can not save a file. 
Anyone have any ideas as to how to get past this issue?  Are there any other NAS drives which will have this type of format available?
Thanks for any support.
Peter