It’s not about pacemakers at all here for the same exact reason you described: if you’re not able to update firmware, you’re able to update underlying OS as well

The problem here is when you sell LTS solutions for $10M thinking you can pay $1000 for keeping your solution afloat for two decades.

It doesn’t work this way. Operation systems as well as frameworks and runtimes, are constantly changing, because the industry is constantly moving forward. The only way to keep up is to constantly (and regularly) update YOUR software too (and plan the budgets accordingly). It’s your responsibility to fulfil your obligation.

After all, you can still run an up to date Linux (or better NetBSD) on a very old hardware, the problem is that you didn’t update your software regularly to just keep up with changing API/ABI, means didn’t invested too much on a longevity of your product