Will the ICS - Issue Calendar Sync for JIRA - work with Office365?
Yes, ICS works with Office365.
However, you should know that Outlook365 doesn’t support manual syncing of internet calendars. This is a general issue and Microsoft won’t fix it. Here is the article, just read the last answer: https://answers.microsoft.com/en-us/outlook_com/forum/ocalendar-oaddtask/calendar-subscription-does-not-refresh/b289bba4-6fc2-4711-85a1-528de6b7ef81?page=11
Funny thing is that Google doesn’t support manual syncing either, which is also requested by users for many years.
Thunderbird / Outlook 2010 / Macmail (all locally installed products) can be synced manually / automatically.