How to add firewall rules to the router programmatically?

[UnitedMarsupials]

My main server -- the DMZ host -- runs software, which monitors a couple of log-files and blocks IP-addresses, from which it sees hacking attacks.

However, I'd like the router to be doing this blocking -- thus protecting my entire LAN, not just the DMZ host.

The DMZ host will still be doing the hack-detection, but, instead of (or in addition to) blacklisting the suspect IP itself, will tell the router to block it.

How can this be done, however? Can UPNP do it? Or is there a REST API?

With an older router I used to be able to telnet in and type commands, but the new one -- a tall white parallelogram -- seems to insist on interactive web-GUI 😞