I recently upgraded to an M1 Mac after my 2016 MacBook Pro died. It's an awesome machine; however, when I tried to install Lightroom 6, I wasn't able to because the installer isn't 64 bit. As a hobbyist who edits photos only a handful of times a year – usually after trips or photoshoots – moving to a subscription model is really costly. What's silly is that I was able to use Lightroom 6 on my 2016 MBP, even after upgrading to Big Sur. I don't blame Adobe for not supporting a product that came out 5 years ago but how nice would it be if they did.
Companies like Adobe don't have much of a reason to cater to these unprofitable use cases. They're going to go deep on maximizing customer lifetime value (CLV) for folks willing to pay more. That's how they keep (or more probably, their only option) for delivering double-digit growth year-over-year, which becomes challenging once reaching a certain size.
Absolutely agreed that it doesn't make much business sense to keep supporting LR6. And 5 years is a long timer in the software world. That said, I wonder if there are companies that do support older versions of software just for the sake of customer delight.
I had a similar issue with 32-bit software with a 16-bit installer. I've solved it by installing it within a VM running a 16-bit compatible OS, then copying the resulting program folder over to the main OS. Have you tried something like this?