Like Jagster, 2gb RAM + 2gb swap is not, in fact, enough for my CLI-driven docker rebuild. Checking further, the only plugins on this install are docker_manager and discourse-prometheus – neither of which would, I expect, put unexpected load onto ember.
If the minimum specs have to change, that would suck, but it would be a lot better than the current situation, where machines unexpectedly grind to death on every upgrade.