Just log off at 5pm or 4pm or whenever you have done your contracted working hours.
I rarely end up in a meeting which goes over my usual working hours. But otherwise I just log off. I don't understand how someone can work longer hours unwillingly when it's entirely in your control.
I guess it depends on how your remote working is implemented. For me I remote in. For others it's a VPN. But either way, cut off all communication avenues until the next morning.
>When someone of greater rank than me in an inconvenient time zone wants to have a meeting with me involved, I have to attend. I’ve practically lost all my mornings from 6am - 9am, 3-4 days a week.
The mistake was attending this even once. Now you've shown a weakness in that you'll attend a terribly scheduled meeting. You need to bring this up, it's not fair to be in work at 6am if that was not the norm before COVID. If your days started at 9am in the office, your days start at 9am at home.