@rfc2822
The issue with published Office365 Calendars is they do not include VALARM attributes - so, of course you won’t be able to sync reminders with ICSx⁵.
Here is an example of a published calendar, that (in Outlook,) has a 15 min reminder, which does not show up in the ICS document.
You can add reminders manually to the Android calendar (after the subscription pulls down events) - but the next sync overwrites these events, wiping out any reminders you may have set.
As a work around, would it be possible to add an option to not remove reminders that have been set manually (if the ics data does not contain VALARM attributes?)