With the current AI/LLM wave SSE have received a lot of attention again, and most LLM chat frontends use them. At least from my perception as a result of this, support for SSEs in major HTTP server frameworks has improved a lot in the last few years.

It is a bit of a shame though, that in order to do most useful things with SSEs you have to resort to doing non-spec-compliant things (e.g. send initial payload with POST).