I've been annoyed too by the lack of Temporal support in Safari. It's supposedly behind a --useTemporal flag, but I've never been able to get flags to work even when launching the binary directly, and I can't find anything in developer options or feature flags settings either so like. Does it even exist at all??

It is enabled by default in STP, so presumably it will launch alongside the 27 releases.

Note Temporal was in the Ecmascript 2026 release back in March.