Our company has a server at every location running a MAMP stack which drives an arrivals/departures/status board. Arrivals are cURLed from a central server, but modifications are handled locally in a way that continues to function if a facility goes offline. Currently, this is done by employees using an Android AIR app which talks directly to the local server on 192.168.x.x. We are trying to replace the deprecated AIR app with a PWA served from a central (https) source that can work completely offline. The main thing is it needs to make some kind of fetch or ajax call to the server in the facility.

What we're running into is the "mixed content" problem. Here's what we've explored:

• We can't use self-signed certs on the local servers. They'll still be rejected.
• We don't want to serve the central app over plain HTTP... and I suspect that wouldn't be a long-term solution either.
• We don't want to host the PWA on every single server, because it would make updates to the app uneven and difficult, and also because the employees would then need to know the current local IP of the server... i.e. it would prevent autodiscovery as we have it now.

I've read what parts of this I can understand: https://github.com/WICG/private-network-access/issues/23

It seems even Plex has a similar problem. But this seems insane to me. Is there no workaround for a PWA served from a central https source to communicate with devices on a local network?