Home Networking

Some wireless devices consider a lack of online access to be an insurmountable hurdle, even if they've connected to a working LAN.

I need to convince these devices to actually try before giving up.

Here's the setup of our band's portable in-ears monitoring rack:

 - a SoundCraft UI rackmount mixer

• a NetGear router (because SoundCraft can't build decent WiFi)
• both are in a rack with misc stage equipment
• devices (phones, tablets) connect to the router as normal
• each band member connects to the mixer via web browser to adjust his own mix

This is basically an airgapped, private LAN, and when we connect devices to it, we are not seeking Internet access. However, we naturally still want to reach the SoundCraft. Sadly, some devices try to "phone home" upon connecting to the router--and when this fails they drop all subsequent attempts to be useful.

I'm looking for advice on overcoming this hurdle, which will involve a setting I currently can't find, either in the device's networking config, or in the web browser itself.

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More detail:

This rig helps our band expedite setup and improve our individual monitor mixes. We connect stage gear to this rack, and a split snake sends audio to the FoH guys. We control ears mixing in real time, and the sound crew don't need to worry about it. Works great, and we love it. EXCEPT...

Some of our devices fail to reach the mixer after connecting to the router, and it's all due to a digital fallacy that's growing increasingly common:

I (device) am smarter than you (human).

Unfortunately this never is the case. Failing devices insist that there's no Internet, and they offer "helpful" suggestions like "check your WiFi password" and "reboot your router."

CLARIFICATION:

ALL devices are able to reach the router.
This is not the issue.

My laptop (MS Surface) always connects without issue--and so do some of our phones and tablets; there's nothing wrong with the config on either the SoundCraft of the NetGear. My old laptop also connected just fine.

I purchased an $80 unlinked phone on Amazon, and it worked perfectly, for several shows, over a couple months.And then it downloaded an OS update, and the next show it refused to connect.I am certain that the devices having trouble are merely laboring under the delusion that there's no conceivable purpose for WiFi other than getting online and checking Facebook--disregarding how our intent is a textbook example contradicting that assumption. As if our sole purpose is to exist online.

This is not a hardware problem, nor is it platform-centric either. The above device is an Android, but a couple guys have iPhones and tablets which also refuse to participate. I've also tried multiple web browsers on each problematic device. Usually Google Chrome is one of them, but we've also tried Safari, Firefox, and Brave.

What I need is to find the setting that basically says

Stop telling me I have no online access, because I don't care.  
Connect to this website anyway: 192.168.blah

I could bring a 100 foot cable and connect the router's WAN port to the venue's network, but

1. that's a silly amount of additional effort to merely sidestep the problem
2. it means we need to ask the venue's permission to access their network--if they even allow that
3. there's literally no other reason we might want external access on this rig
4. we've played outdoor festivals where a local network wouldn't be available anyway

I feel like I've exhausted my exploration of the various options, in both browsers and device settings. But hopefully someone reading this knows the magic words.

Ideas, anyone?

Thanks for reading.