Some quick basics. Mesh as such doesn’t refer to any specific tech, standard or frequency, although there are such for creating mesh networks. Mesh is just a description of how nodes (devices) in a network are connected. A couple of good articles for bacground:
There are other ways too. Using your L5 as a wifi-hub is kinda the the minimum example to create a connectivity for others. You all still need a bit of configuration for the data to flow to all and an app (how a bout talk? 
) to exchange messages. The obvious benefits are that you have your own ad hoc network that is free and private (depending how you’ve set it up) and works within the area your devices are able to broadcast - even in remote areas or when other networks are down.
When you get down to it, there is physicaI data packet transport layer mesh and an application layer mesh but at user level you may not notice. I suppose a mesh network could be created with Wifi and some app/server running that takes care of relaying the messages to others. There probably is something like it already.
In regards to L5 there was talk of for instance using LoRa, which would need a separate module (think modem or wifi). The other option is, that it’s external. Some commercial devices act as hubs and your phone connects via BT (or wifi), while it uses something more powerful to create the mesh with others like it. BT takes less energy and the device connecting probably has it’s own battery for those signals. This is also one of the neat features: messages may be relayed beyond the range of a singe device via others in the network. Again, very useful for a groups internal communication in a limited area - gives it a bit of flexibility.