Sprich oder scheiss bustaben dammit wir dir lesen kann.

His router is tri-band though meaning it has 2 5ghz transceivers.

Unfortunately, for many models - like the Linksys WRT 3200ACM - that second antenna (technically the third one if you include the 2.4Ghz one) doesn’t function at all without the manufacturer’s firmware. It’s a dead stick with any third-party firmware, and is 100% software-enabled.

I have found this fact to be reliable whether it is DD-WRT or OpenWRT, and across several different manufacturers including Asus and D-Link.

That makes a lot more sense for your setup, then.

Fail2ban bans after 1 attempt for a year.

Fail2ban yes; one year, however, is IMO a bit excessive.

Most ISP IP assignments do tend to linger - even with DHCP the same IP will be re-assigned to the same gateway router for quite a number of sequential times - but most IPs do eventually change within a few months. I personally use 3 months as a happy medium for any blacklist I run. Most dynamic IPs don’t last this long, almost all attackers will rotate through IPs pretty quickly anyhow, and if you run a public service (website, etc.), blocking for an entire year may inadvertently catch legitimate visitors.

Plus, you also have to consider the load such a large blocklist will have on your system, if most entries no longer represent legitimate threat actors, you’ll only bog down your system by keeping them in there.

Fail2ban can be configured to allow initial issues to cycle back out quicker, while blocking known repeat offenders for a much longer time period. This is useful in keeping block lists shorter and less resource-intensive to parse.

Do either of the options you mentioned provide custom nameservers? As in, the ability for ns01.yourdomain.com to resolve to your account on their DNS servers?