Not sure where you’re based but some of the mid-sized companies definitely do hire outside of the US and offer equity (typically places where they have a company presence so they can employ you, and I guess they’ll probably try to have people in sensible time zones) and are remote-first. For example, I’m based in London and my last job was with MongoDB and that was fully remote in EMEA.
Check out angel.co and look for remote startup roles - I've worked with two US startups from the UK prior to moving out here. Some are happy with extra experience & lower end of salary while you'll still have a good multiple.
The alternative to that is contracting - London is a great place to look for that.