ReadyNAS 424 and CenturyLink C4000XG

I use ZeroTier  (see ZeroTier-as-a-ReadyCloud-replacement).  I used it instead of ReadyCloud even before it was shut down.  Depending on your requirements, something like OwnCloud or NextCloud can also be useful.   But for that, I find it best to run it on another platform and set up ReadyNAS folders as external folders.

JordyB wrote:

Is FTP a decent method?

No, because it is unencrypted.  Your login credentials are sent over the internet as clear text.  You could set up FTPS - the NAS has an option to require encryption when you use that.  You will need to set up a passive port range - I suggest 4 passive ports for each expected connection.  These should be in the range 49152-65535.  You need to make sure you use a strong password.

Note you would also need a dynamic DNS service (DDNS).  Centrylink Routers do support this:

• https://www.centurylink.com/home/help/internet/modems-and-routers/advanced-setup/dynamic-dns.html

noip.com is a DDNS provider that still offers a free DDNS account.

All the ports (primary and passive) need to be forwarded to the ReadyNAS in the router.  Also, it is good to reserve an IP address for the NAS, in order to make sure the NAS always gets the same local address.

• https://www.centurylink.com/home/help/internet/modems-and-routers/advanced-setup/dhcp-reservations.html

All ReadyNAS are end of life, so you need to assume there will be no more security updates.  You could set up an always-on PC that has the NAS drives mapped to drive letters.  Then install NextCloud or OwnCloud on the PC (and not allow direct connections over the internet to the NAS).  That would give you more features (similar to ReadyCloud).