Bridge mode being the important half deserves more emphasis, because double routing fails in a way that looks like everything else.
Symptoms: some devices reach the internet and cannot reach each other, port forwarding appears configured and does nothing, and video calls drop for one person on the network and not others. Every one of those reads as an application problem and none of them are.
If you are adding your own router, check the provider box is actually bridged rather than assuming the mode you selected took effect. Mine reverted after a firmware update and I spent an evening on it.