The thing of interest is that although the DNS-320L, and the other D-Link NASes, is EOL (End Of Life), there are more than 90,000 devices still operating out there!
The bad thing here is that many manufacturers, even big ones, tend to forget “old” products and drop support for them. Usually it’s a market/business decision, but this is what happens with closed systems :-(
Quoting from https://www.dlink.com/uk/en/products/dns-320l-sharecenter-2-... :
>> This product was phased out on: 13/11/2017
>> This product's last date of support is on: 13/11/2019
Being an owner of 320L, I don’t expect D-Link to offer us an updated firmware any time soon.