It's kind of ironic to be using a device made to display advertising to combat advertising itself.

Digital signage isn’t really about advertising. It might be used to eg show departures at an airport/bus station, or show schedules for different rooms at a conference or fair/exhibition/show. Other common uses are to show a few slides on a loop, eg in a reception area of a school showing the school’s achievements.

The uses you mention are common, but digital signage for advertising is big in retail. It's almost always trying to drive you to purchases.

Some network operators run 3rd party advertising to offset costs of running their network.

Also, if you see a sign at person level in a public space there's a high likelihood it's collecting demographics information on (age, gender, ethnicity - via video image processing) on everyone passing by while also trying to identity the mobile device in your pocket to geotag your advertising identity.

I work in a company that provides general interest "filler" type content for networks to display - news, weather, sports e.g.

Don't those signage panels have godawful refresh rates though, like 10hz? I believe it's part of the reliability tradeoff

They used to but now since video is popular they don’t. But they have poor blacks.

And you can view some outdoors in the sun of high noon

Those are usually eye-wateringly expensive but amazing.