If you really want to, you could check out Evolt’s browser archive:

https://browsers.evolt.org

It‘s got over a hundred ancient web browsers. I suspect none of them support SHORTTAG NET though.

Good idea. I remember I have done some research about this in the past when I tried to trace historical arguments for the infamous "should there be a space before slash in void tags for the best compatibility"

    <br/> vs <br /> (vs <br>)
discussion, but didn't get much far then (https://stackoverflow.com/a/30880386/540955).