On ECRs, long-form-outputs, and the non-portability of outputs for REF

There has been a lot of angst about the newly proposed non-portability requirements for REF2021 and beyond, particularly from ECRs. I want to say upfront that I do not want to disparage such worries; I speak from a position of privilege, having a permanent position even though I am, by RCUK standards, myself an Early-Career Researcher. I do, though, want to set out why I think these fears are misplaced/over-blown.