I can tell you what is the fucking problem and it has nothing to do with ip range or whatever.

It is all because of encryption with all these damn routers. When you had nothing much connected, the laptop negotiate highest speed with the router using WPA3. Then once you got lower end devices connected, the damn router will lower the encryption as backward compatibility. You can either goto the saved wifi network setting and set the encryption as WPA2, type your wifi password again. Or goto into your router, and change encryption to WPA2 only instead of WPA2/3