Can you try tailscale or set up a reverse proxy?

For the latter, buy a domain and then use the cloudflare free tier to route to your IP. A simple docker container can run every 60s to update your IP with cloudflare

Connect PC1 to the router and you’re done.

Currently PC1 is on a different network since it connects directly to the modem

Why do you regret that choice?

I have a UniFi system: APs, switches, CKG2, Gateway. I’m looking to add CKG2+ and some POE cameras

You need a license for Cisco / Meraki APs

DynDNS doesn’t solve the problem.

DDNS acts as a proxy service between the Internet and your home network. It’s a simple way to have a service running at home (like a Minecraft server) and make it always available to users outside of your home. The would go to a website like “rafa.dyndns.com” which would forward their traffic to your home network. The magic is dyndns is changing the route from their domain to your home network without anyone knowing about it.

The ISP cycling your WAN IP lease every 12 hours is unusual and tells me either A) they’re not a sophisticated ISP or B) you live in an area with an unstable backend.

For an example of B, they might be doing infrastructure improvements in your area which means they have to restart the nodes regularly.

Unfortunately for you, there’s not much to do about your home network connection stability if the ISP is restarting the nodes this often.

I’d suggest either finding a new ISP (if possible) or talking to someone else at the ISP (Tier 2 or Tier 3 Support) about why this is happening and if they have a long term solution

Obsidian

You could put the ATT router into bridge mode and use only the Asus router.

You could run the parallel networks, but ensure they are on different channels to help reduce the interference. The devices may manage their channels automatically, but YMMV

You should not use the same SSID on two different networks. That will be a nightmare.

Check out PiKVM, but I don’t understand why you can’t use SSH or XRDP

Blue Iris is open source

UniFi Protect is closed source but self hosted

How is it fraudulent if they admitted the mistake and refunded you?

Sounds like a legitimate billing error caused by unusual user behavior

With nginx, you shouldn’t need to forward any ports beyond 80/443

For really simple auth, check out Cloudflare Zero Trust