By mobile do you mean relocatable or GW’s that are providing service whilst vehicle (train, truck, car etc.) moving.
Relocatable is generally ok - you have to be able to set up test gw’s check coverage then reposition to optimise if needed - prefereably deploying for extended periods of time each time (think weeks & months).
In isolation - say on a container ship or cruise liner - were GW(s) servicing the then local traffic associated with that large vessel, again considered ok - indeed Marine IoT is an emerging category for the industry and has been much discussed on the Forum esp in context of 2.4Ghz LoRa/LoRaWAN
Some private networks use mobile/on vehicle gw’s e.g for the rail industry - again servicing local on vehicle traffic or helping to capture trackside data whilst in transition and assisting in very remote area.
Generally, however, and certainly in the context of the TTN Community such mobile GW’s as in active whilst in motion are discouraged as they are potentially disruptive to other users. Best practice for (especially static) nodes is to enabe ADR - the signal strength data for that can be purturbed by mobile GW’s making the NS think the node suddenly is in range of a stronger GW than normal, forcing node to change behaviour, then causing signal loses when GW moves on or similarly a GW will report a deminishing sign which again causes NS to change Node behaviour to compensate - burning battery and reducing field life. So whilst Mobile is valid in a priviate network where such behaviour is understood in the context of the Community network they are highly discouraged for obvious resaons…