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Need basic routing help for router behind modem

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Just added a static IP to my cellular (CGNAT) account in hopes of viewing my LAN cameras remotely.
The modem is functionally limited, so I kept my 68U behind it. I've enabled port forwarding and tried a DMZ, but so far no go. It worked for years when I was on DSL, so I'm sure of the nvr/port forwarding/Windows firewall configs. Do I need a static route? Could CGNAT still be an issue?

   modem            router                nvr
The safest way is using the vpn server built in to the router. Manually Assigned IP around the DHCP list for the cameras.
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I had attributed the problem to CGNAT then and gave up, but forgot I'd asked here before. Sorry.

As before, the modem has no routing features or bridged mode, only a DMZ. I guess the VPN solution would also be blocked by this?
Yes a VPN would suffer the same problems.

But your original idea from before should work. Put the Asus in the DMZ of the modem, and then do your port forwarding on the Asus.

If that doesn't immediately work, with the same configuration, enable WAN access to the Asus (Administration - System) and see if you can get to the router from the internet. Remember to turn off WAN access after you've finished testing.
Browsing port 8443 on the Asus in the modem's DMZ works.

Do I need forwarding in the modem?
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I turned off wifi on my phone and am coming in from its data connection

Do I need static route from 0.x to 1.x?
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I turned off wifi on my phone and am coming in from its data connection
OK I got confused because you initially posted that it wasn't working and then edited your post to say it was.

Do I need forwarding in the modem?
You either need DMZ or port forwarding, not both. As DMZ is actually the same a port forwarding all ports I suggest you leave it in DMZ mode for the moment. If you can get it working then later you can change it to forward individual ports.

So at the moment you know you can get to the router's WAN from the internet, So now you have to setup port forwarding on the Asus to get to the device on your LAN.

P.S. Turn off WAN access to the Asus again now that you've proved that part.
Jeez. In the process of trying different things, I had put an entry in "port mapping" as well as port forwarding. Deleted that and all is well.

Thanks loads!
That's good news. Does it now work with you forwarding the individual port rather than having the DMZ?

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