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:
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:
https://archive.org/details/modern.ie-vm