Good morning,
I am not a very good expert in configuring Mikrotik, but quite enough to manage basic setup. I already have some LTE routers connected to alarm systems and they work great.

I am going to get a new router ( model 5009 ) to replace the one provided by my ISP.
I have a FTTH line and a optical termination \ Nokia ONT @ 2.5 Gbps, but capped at 1 Gbps according to my subscription. To the ethernet port of the ONT there is the WAN port of the ISP router. I also have LTE usb stick with a public IP SIM card, to be used for backup purpose in case of faults on the fiber.

My goal is have a Mikrotik to replace the ISP router:
- Internet traffic runs on a specific VLAN, so the Mikrotik should manage it.
- Voice traffic runs on a second VLAN and this should be forwared to a specific LAN port, UNTAGGED
- I have 3 ports opened so incoming traffic from the internet to such ports should be forwarded inside my LAN to 3 different hosts
- in case of no internet on the WAN port (the one connected to the ONT), the router should bring up the LTE USB dongle ( model k5160) and reroute there.
Since I have a public IP on both the FTTH and the mobile data, I need to access my LAN from outside even in the case the router is running on mobile.

Do you see any problems in managing this landscape with a 5009 ?

Thanks

From the little I know the plan seems sound.

The only possible issue could be related to the compatibility of your existing USB LTE device, I have seen some reports of problems with some devices on USB3 ports (like the one the RB5009 has) but not (AFAIK) a definite list of which one have issues and which ones work fine, the list here:
https://help.mikrotik.com/docs/display/ROS/Peripherals
is about supported models by RoS (and the K5160 is there alright so it is supported), but still it has to be tested in practice.

The only possible issue could be related to the compatibility of your existing USB LTE device

I had a look days ago to the compatibility list you mentioned and I see there the k5160.

Anyway... if someone can suggest a "certified" USB LTE stick... more than welcome... I can get it, but I do not know if this exist