Best way to export ticktick to proton?

I've used ticktick for a little while, but now I am retired I find I don't really need all its features. I am already paying for proton mail and the calendar with that seems quite adequate.

What is the recommended way to transfer tasks from ticktick to proton? I have a handful of calendars and some repeating tasks, that is about it. Worst case I can just do it manually, but I would prefer to export and import to avoid missing anything.

I realise ticktick isn't that expensive, but paying $35 a year for the rest of my life seems a bit silly.