There's little usable information about CSS @media queries for EPUB and Kindle out there. And what there is, is often wrong or outdated. Just a couple of weeks ago I was struggling with width and height as reported by iBooks (now called Apple Books) on iPhone and iPad: they're certainly not device pixels, and they're not what's quoted on various blogs and community sites.
And before you state the obvious: I'm not advocating the use of pixel based breakpoints, but sometimes it really helps to know what kind of device a story is read on so you stay in control.
In the end I made a small EPUB to figure out dimensions and other device facts, and that gave me the idea to ask you to lend a hand so I can collect and list the data gathered. Hopefully this gets enough traction that it stays current even when device updates or new devices pop up.
The "Ebook @Media Queries" EPUB (and an equivalent Kindle mobi) is at
https://ebookfonts.uk/fdir/free-ebooks.html.