Hello, Jonny.

iPhone: Calendar → Calendars → ⓘ next to a calendar → Public Calendar on → Share Link → Copy. Paste here. webcal:// is fine.

Apple Reminders lists can’t be published. Make an iCloud calendar called “To-dos”, publish it the same way, and add tasks as events on their due day. Start a title with ✓ or [x] to mark it done. Undated tasks: use a VTODO feed.

iCloud blocks direct browser reads, so the page goes through a proxy. Your own Cloudflare Worker (see README) is the reliable, private option. {url} = encoded link.