I hear ya, I bought a copy of Office back when they were allowing employees of their corporate accounts to do so at a discounted price. Now it won’t run because “no longer supported”. Pissed me off enough I just learned to use Open Office instead. Screw Microsoft.
I have purchased Microsoft Office Licenses on eBay a couple times for a few dollars. I never expected them to work, but so far they all have, and they have kept working. The actual software is downloaded from Microsoft’s office.com website. You use the license key to create your account. So far none of them have expired or stopped working. After about a year I managed to lose the password for one of the accounts that I created, but the seller fixed it for me when I sent him/her an email.
I also use Open Office and have had no issues. I feel the same about microsoft.