Sophos Sandboxie builds and prior builds of classic Sandboxie
Whoa--I was going to put down Internet Explorer and guess what? You can still dredge it up, even in 21H1 preview which is what I'm running now. So it's not defunct yet--it's alive, it's alive. But its performance is terrible compared to what it was back in the day.
For a short time, running IE in Sandboxie on Windows 10 was nigh perfect until the legacy Edge came along. I then ditched IE for Edge and SBIE couldn't work with that, of course.
I'm writing this from IE. It can't compare to the modern browsers now so in that respect, it's defunct. But it's still acessible in Windows 10.
edited to clarify specifically Sophos builds of Sandboxie--nothing else.