I'm confused about the role the two different devices play...
- It sounds like the C7v2 is the primary router and that it is running OpenWrt. Is that correct?
- The DIR1935 is not supported by OpenWrt, despite 'almost' being possible to do. But it probably never will be because it only has 8MB of flash memory -- not enough to support future versions of OpenWrt and not likely to be added to the current release. So I don't know what VLAN capabilities it has, but if it does actually allow you to specify VLANs, you may be able to work with it... depends on the details. But what does this device do in the context of your setup?
Are the cameras wired or wireless? Do they connect directly to the C7v2 or to the DIR1935 or some other device?
Let's take a look at you config:
Please connect to your OpenWrt device using ssh and copy the output of the following commands and post it here using the "Preformatted text </> " button:
Remember to redact passwords, MAC addresses and any public IP addresses you may have:
ubus call system board
cat /etc/config/network
cat /etc/config/wireless
cat /etc/config/dhcp
cat /etc/config/firewall