As a self-hoster for over a decade, setting up SPF, DKIM, and DMARC are pretty much once-and-done and free, so there's pretty much no downside. I'd be shocked if most self-hosters haven't set these up long ago.
A lot of places don't accept outgoing SMTP traffic at all, some allow it for personal usage and finding someone who accepts you sending lots of outgoing SMTP traffic is gonna be really hard, except if that host already hosts lots of already spam-marked IPs.
List-Unsubscribe-Post: List-Unsubscribe=One-Click