[Petra-Kathi]

One of many setup guides to obtain a completely local network might be the following:
https://www.tomshardware.com/how-to/rasp...cess-point

Presently I do not have a spare Raspi to check it out, though.    (All my installed ones already serve defined purposes, and I don't want to tear the functionalities down.)

An alternative might even be to use an older, unused internet router, even though such a device is somewhat bulkier than a Raspi with a powerbank. You'd typically need a(nother) power socket to get it going.

Petra