It depends what make and model these routers are, but u/jerwong’s advice is right.
If you want some key words and phrases to figure out how to set it up, you’re running is two subnets, two DHCP servers and an internal NAT firewall on your second routers which is keeping the two networks separate. You want everyone on a single subnet (or separate subnets with a subnet mask to cover both), a single DHCP server (or two in the subnet mask solution could work) and to remove your internal NAT firewall, which will be an outcome of the first two things.
If all this is foreign to you and you don’t want to learn, it’s probably best to just spend some money on the problem.
The ‘right’ way to do it is to fix the main network so that it works with your Qyest.
Perhaps self hosting isn’t for you? Have you thought about watching Netflix on your Windows 11 tablet connected to your ISP-provided router?