ECS is worth a mention

"Open source" stratified long ago to incorporate most of what we used to consider enterprise crapware as the default style of project that gets any exposure. They're still the same teams of 9-5s pumping out garbage, it's just that the marketing and licenses changed substantially. Getting paid to "work on open source" might have had some edge 20 years ago, but I can only think of 1 or 2 companies today doing what I'd consider that to have meant in the early 2000s.

As for ECS lock-in, the time saved on a 1 liner SSM deploy of on-prem nodes easily covers the risk at some future date of having to port container definitions to pretty much any other system. Optimistically, assuming 3 days of one person's time to set up a local k8s, ECS offers about 450 node-months before reaching breakeven (450 / 5 node cluster = 90 months, much longer than many projects last before reaching the scrapheap). Of course ECS setup isn't completely free, but relatively speaking it may as well be considered free.