Most apps integrate with reminders in some way, but only import from there. I am also looking for a long time now.
The only app that comes to mind is Obsidian with the „Remotely Save“ sync plugin. I use it for notes but you can use obsidian for todo lists.
Thanks for the info, it just seems so strange that there are loads of options on Android and so few on IOS. Everyone seems to have designed their own cloud back up system complete with subscription service.
It does look like "2do" is an option but it is £9.99 and there doesn't seem to be a trial
I use 2Do on my iphone and like it. I'm pretty sure i haven't paid for it. At least I can't remember paying, and can't find a receipt either in my mails nor the appstore.