So this is a huge issue with companies right now freaking out about compatibility. Microsoft Edge still isn't full compatible with websites designed for IE. Since Microsoft is putting so much of its stake into Microsoft Edge built on Chromium it needs to incorporate IE some how. So Microsoft Edge (Chromium) IE mode is in fact built into the new software. Make sure you have the newest version as of this post and you can have it.
https://winaero.com/blog/enable-ie-mode-chromium-edge/1. Update Edge Chromium Dev to the latest available version (see the list below).
2. Type edge://flags/#edge-internet-explorer-integration into the address bar of Edge.
3. Enable the flag Enable IE Integration by selecting IE Mode from the drop down list next to the flag's name.
4. Restart the Edge browser when prompted.
5. Right-click on Edge Can/Dev icon on the desktop and select Properties from the context menu.
6. Modify the Target text box value by adding the "--ie-mode-test" option after "msedge.exe".
7. Now, launch Edge Chromium using the modified shortcut. You'll find the menu > More tools > Open sites in Internet Explorer mode option
Note that now the browser shows an info bar with the following text for the IE Mode tab.
All sites in this tab will be opened in Internet Explorer mode
You will need to repeat step 7 for anytime you want to use the IE mode.
Keep in mind it's not really recommended to use this feature but it's absolutely NEEDED for work or for a specific test then here is how you would do it.