Honestly this would probably work. Know how to do that?
Discussion
My first pass at this would be a static html page served kiosk mode in a browser that uses JavaScript to cycle through divs or iframes of the 3 sites every few seconds.
If there's some reason that can't be done due to CORS or clickjacking prevention then id pair it with nginx to proxy the requests altering headers as needed
I'll try this out with a pi3 that has a display attached via HDMI and see how it turns out
Awesome, thanks for the input
Made a small page to test this
Gist is available at
https://gist.github.com/vicariousdrama/5ca7d945d7af07dcb44e60f5bb9af7c9
and here are results..
Can cycle through displaying iframes as expected.
But iframe deniers won't load in the browser due to headers being passed down ( mempool.space and Clark Moody Dashboard are some setting the header content-security-policy: frame-ancestors 'none')
Options are
1. Setup a pi per display with X, browser auto start to kiosk mode for one site
2. Single pi single display rotating between sites that don't block (can use the gist for this)
3. Same as #2 but use browser extensions to remove/ignore the response headers that cause client not to load in iframe
4. Same as #2 but use a server intermediary to proxy requests with url rewrites that drops the headers
For all the above, a pi3 is fine if you can get them or else just a low cost computer with HDMI out to TV
Holy crap hahaha did not expect this. Gonna try this out later when i can. Zapped you anyway!
If the iframes work, you wouldn't even have to cycle. Put them all on one page, taking a quarter of the size each and you got your split screen mode