How's the UX? I'm looking for something along the lines of my device uses bluetooth to scan for local devices, I select the ones I want to form a mesh with, the owners of those devices confirm, then we're in a hi-speed wifi mesh.

Meshtastic UI is pretty far along that path right now. You can purchase a device for like $50ish that gives you a few miles of reach in the right conditions and has a decent UI built in (on the latest rev). If you want to run firmware on chips and use UI from your phone over Bluetooth you can run on like $12ish per endpoint.

It doesn't result in a high speed local network I could use for transferring files or hosting a LAN party though, right?

With the new mesh over UDP features in the beta, you can set up a long range directional WiFi mesh, and only use LoRa for the last hop.

LoRa itself is sub-mbps though.

In so far as communicating without going via the internet. This would work by 2 or more people sharing the same wifi network, but they they talked to each other would be over Reticulum?

Can a wifi mesh with no internet connection be made between different routers / access points?

Really I am wondering if people cooperating by operating wifi areas t could expand quickly in more populated places.

Perhaps the trick would be to run them all the wifi networks fully open?

Yeah basically how does one create a city wide mesh with a few hundred people involved?

Meshtastic will too, if you get the 2.6 version. You need the beta version of the Android app to enable it because it's so new though. But it does work, and it's rather easy to receive the packets in Python and do all kinds of interesting routing from there.

Interesting...

Does this mean Meshtastic is evolving toward a more general purpose system with multiple interfaces (not only LoRa) and other applications (beyond messaging) ?

That would be pretty cool!

It seems like it's really only missing a few things.

The big things needed for IoT, as I see them:

* The ability to use it as an Arduino library

* Global routing without preconfiguring the relays, as in Amazon Sidewalk or The Things Network

* Some more generic abstraction for telemetry and control, as in Mobus

* The ability for a firmware to define custom config options that the app can set(Something like a JSON schema, maybe local only because of bandwidth)

I actually started a few discussion threads on some of these, and did a few proofs of concept for the P2P global routing.

But I don't particularly want to spend much time on it unless it seems pretty clear it might actually get merged one day.