Honest question. I’s < .5% market share and retired since 2023.
First, the Microsoft browser these days is Edge, not IE. IE is dead.
Second, if you want, or wanted in the past, to test on Internet Explorer without a Windows computer, you could just virtualize Windows. Windows can be legally virtualized on any hardware and on any host operating system.
Starting from 2013, you didn’t even need to pay for a Windows license to do that:
You would still need a VM for that.
Just like you can get a macOS VM, plenty of ways to get them.
How can I run a macOS virtual machine LEGALLY on my Linux or Windows machine?
As for people working in a serious professional corporation that cannot condone casual piracy, buy a Mac mini and expense it, or get an account on MacStadium.
Naturally Chrome forks work everywhere, given that so many devs have sponsored Google's takeover the Web.