How to config RouterOS + GPON Module as a replacement for ISP Fiber Modem ?
Can work ?
Ask your ISP if they support this and want to help you with the registration.
See below in the forum how someone else got the reply that his ISP only support the device they supply.
My ISP support GPON Module.
How to config RouteOS ?
Same thing. You need to get info from your ISP on what configuration you need to apply on your router(vlans, static address, dhcp, etc).