"This would be a good a time as any to enable Enterprise Mode to make the browser behave like older versions of IE for those pesky corporate intranet applications that insist on a specific incarnation of a specific renderer."
Or just finally rewrite those obsolete pieces of junk in something even vaguely modern with proper security controls.
Sorry, but if your product is "IE / ActiveX -only" in this day and age, you are failing at IT, it's as simple as that. Not just from a "Ooops, that's a bit old" viewpoint but because it's useless cross-platform, it's inherently insecure by design, and the warnings have been there for 10+ years.
"Legacy software" you cry? Yes. So ditch it. Like you should have before it became legacy. If that costs, then that costs, but it's like expecting a 1960's Morris Minor to be the company car and I bet that doesn't happen.
Honestly, if you even SAY the words "Internet Explorer" nowadays when on a tech support call - unless it pertains to finding out if I'm using some obsolete piece of insecure junk - then you've failed. If that's the customer's ONLY option to use your product/service, you should really get out of the industry.
I honestly judge our banking supplier (Barclays) SO harshly because their online smartcard-based super-duper sign-in to authorise payments for a multi-million-pound business has a minimum spec of "IE 10, or Firefox ESR"... and it literally doesn't work on Chrome at all. That's just so ridiculously stupid nowadays that I can't fathom why we give them the business. And that's orders of magnitude better than "only runs on IE".
If you are at all affected by this, for anything, at all, whatsoever, then you are using dangerously out-of-date software (whether "just internally" or not) and have been for years. Try doing something about that, this time round, rather than enabling backward-compatibility (a.k.a. "please pretend to be as useless and insecure as you used to be") and propagating into even greater levels of ludicrousness.