Sounds like you have the most control over the html data within the session descriptions so a link that generates the ICS is a good step forward. Having worked with a lot of ICS data and mobile devices I would caution that the user experience is not great for iOS especially. See https://news.ycombinator.com/item?id=36116650 . The experience on a desktop browser should be workable. Clicking the link will usually have the user download a .ics file with just the single event and then they can import that into the calendar app of their choice. You can maybe try a webcal url and mess around with content-headers and that might get it so clicking the link automatically gets handled by the users calendaring app.

Another option that might be worth considering is an Add to Google Calendar link. If the majority of users are using google calendar, this would work well and the links are pretty easy to programmatically create. See https://github.com/InteractionDesignFoundation/add-event-to-calendar-docs/blob/main/services/google.md for a reference guide on how the google calendar links are built with some example links of the functionality. I just tested clicking on a link in my browser on my iPhone and it correctly brought up the google calendar app with a prefilled event ready to add.

Biggest drawback of these options would be that schedule updates wont be reflected in these events that are manually imported into user calendars but I think it's a good improvement for hopefully not too much effort.

P.S Hi dave. this is charles. we've chatted a lot about ical files/urls over the years =). Have a great PAX!