I'm running an INDI/Ekos imaging setup on a Pi4 under ubuntu-mate 20.04

The Pi runs KStars and Ekos and I control via TeamViewer from a distance on a laptop.

Normally, I want to have all this connect to an established "infrastructure" WiFi network in my remote cabin (no internet).

But for portability, I'd like to set ubuntu to "fail over" and *create* its own stand-alone WiFi network if and only if it doesn't find the existing network at the known SSID for the cabin.

I am trying to do this in NetworkManager. I create a new WiFi network with the name "hotspot" and give it the SSID "hotspot." I assign it to mode "Hotspot" (or should it be "Ad-Hoc"?).

I give this new network a lower priority than the existing one, so it never gets created as long as SSID="cabin" is found.

Then I need to figure out settings for DHCP or not? Gateway? Nameserver?

What I intend is that if I plug in the pi4 in the field and there's no SSID="cabin" then the laptop will automagically see a new SSID called "hotspot."

I must be doing something wrong because so far i can't see the new SSID from the laptop at all.

Can somebody help me make this work?

Many thanks!
Scott

I guess another way to ask this is:

"What's the difference in ubuntu between WiFi network modes Hotspot and Ad-Hoc?"

and

"How do I set one up so that my laptop can access ubuntu without a router?"

Ad-Hoc wifi network is without central access point and each device communicate directly with each other. Hotspot mean that device turn into wifi access point and serve others clients connect to it.

I think you will need write some scripts for this fail over because I doubt that there is some GUI tool for this.

This is one of the features for StellarMate and probably other images out there.

Just assign lower priority to a hotspot connection. It will start only if higher priority wifi network is not available