Just to clarify this: From my experience, the cost to maintain this would probably be 4 full-time very competent system software engineers, because pretty much every pieces of Android will be fighting against such a use, and Google certification for Android devices will forbid most changes you'd want to do to have Android allow it. Also, you'll be much more likely to delay the project (either release or even simple upgrades, because Google's tests are often upgraded with new tests), making it liable for all other features as well.
So yeah, it's sad it went away, but I can't blame Samsung for it.
Sadly the experience wasn't fluid enough to make more people interested. And I think hardware were just one generation or two from being in a sweet spot of making it reliable and fast enough for most.
Still have my hopes of it coming back
It went away with the upgrade to Android 10 [1] probably because Samsung didn't want to spend money when only a few people was running it.
[1] https://www.slashgear.com/samsung-linux-on-dex-is-dead-here-...