Instead of directly triggering RSS/webcal/email - provide a popup with interstitials and options across multiple tabs with clear explanations for what happens on each.
Provide QR codes on desktop so users can easily trigger subscriptions on their phones as well.
Provide special guidance for Google Calendar users, Android users. Also do some user-agent detection.
Test this well not just across devices (samsung/pixel/android/ios/macos/windows), but also with a combination of calendar apps being installed and not-installed.
Instead of directly triggering RSS/webcal/email - provide a popup with interstitials and options across multiple tabs with clear explanations for what happens on each.
Provide QR codes on desktop so users can easily trigger subscriptions on their phones as well.
Provide special guidance for Google Calendar users, Android users. Also do some user-agent detection.
Test this well not just across devices (samsung/pixel/android/ios/macos/windows), but also with a combination of calendar apps being installed and not-installed.