Heads up: "Update Required" prompt in the Sonos app

As far back as I can remember, there’s been a loose connection between the app version (controller) and what is running on the system (speakers). That extends back to the late 2000s. I’ve had to call in in the past to get an un-updated device I’d been charged with maintaining up to a version that could be updated by the current controller and subsequently updated without a call. This would have been long before the S1/S2 split, back around 2015 or so. 

I'm not unhappy with the way things are and have been working, where new app versions require compatible firmware but the firmware will continue working, at some level, with older apps.

The rare cases of systems with no Internet connection to update firmware shouldn't be a reason to impact a majority of users.

Might be nice to have a way to update firmware over a cellular or other connection if there are enough users that would help to be worth the investment.

Not the full use of the system that isn't (below) supported, just a firmware update tool that can work over otherwise unsuppoted connections. Maybe a tool to download/cache the files needed for updating with no network connection necessary? (My router offers that as an update option and it is quite handy.)

https://support.sonos.com/en-us/article/sonos-system-requirements

​@Smilja Sonos S1 would like a word. 

Just ignore it folks, don't take the bait.

With respect to remotely located devices, beyond Internet coverage, it would be possible to develop an application that could be loaded on to a computer or portable drive that could then update the remote system, but I don’t think that the development cost could be justified.