Your StayTuned feed is a standard iCalendar URL. Every major calendar app supports it — they just hide the option in different places. Pick your app below.
Go to calendar.google.com on your laptop. The phone app doesn't expose the 'Add by URL' option — you'll add it once on web, and your phone will pick it up automatically.
Hover the 'Other calendars' row and click the plus icon (+) that appears next to it.
A small menu pops up. Select 'From URL' — not 'Browse calendars of interest'.
Paste the .ics URL you copied. Within a few seconds the calendar appears under 'Other calendars' and your events show up across all your devices.
The URL is a plain RFC 5545 .ics file. Any standards-compliant calendar app — Thunderbird, Fantastical, Proton, etc. — will accept it via a generic "subscribe from URL" flow.