Questions about Ubiquiti UF-RJ45-1G: SFP to RJ-45 module

You can also use ports 8 and 9 on the UDM Pro. But if you want to use them for other devices (as a switch port), you can use this SFP module to make ports 10 and 11 usable as a copper WAN.

Branded gear, like HP, Cisco, Juniper usually don't like 3rd party accessories. (a.k.a. lock-in). My Cisco SMB switch does not tolerate this module either.

Yes that should work

In short: most likely yes! It's worth trying. In more detail SFP transceivers generally are quite reasonably defined and abide to sane standards. There are cases where SFP manufacturers went out of their way to implement features of their SFP modules in a fancy pants way expecting special initialization commands in exotic ways which prevents them from working unless specifically recognized and specifically talked to by the device they are being used in. And there are switch or router vendors that went down the full out dick road, maintaining whitelists of specific SFP modules and just plain out disable modules that are not explicitly whitelisted although there is absolutely no sane technical reason for it. Cisco is kind of one of them because they love selling their branded Cisco modules made by the same couple of those major vendors anyone has them manufactured by for 4 times the price. But in general in most cases most combinations should just work fine when using straight dumb optical or Ethernet transceivers. Not with fancy special SFP devices like g.fast modems built in SFP form factor for example though. If you would use a Catalyst Series switch from Cisco you could use "service unsupported-transceiver" that should allow it to work for sure by just disabling Cisco's whitelisting dickery but I suppose there's no such thing on your model.

No, that is not possible. You need a G.fast-capable router that can deliver the Internet signal directly to the WAN socket of your own router as a gateway, e.g. Vigor 166 Gen2 or Zyxel XMG3927.

Yes, e.g. as uplink ports for cross-building cabling, since fibre optics are potential-free, you don't have to worry about the earth.

Hello Yes, there are then 10 x RJ45 and also works with conventional RJ45 as a remote station. By the way, you do not have PoE on the ports with the module. It doesn't have to be Ubiquiti SFP, other manufacturers have also been used and according to Ubiquiti forums this has worked.

Exactly, with this module you have a regular copper RJ45 port and can connect devices via Ethernet cable.

That module is only compatible with a 1 gb connection. I had the same problem. I solved it by putting a small gigabit switch between the sfp module and the wan.