I used to insert hyperlinks in ics file using x-alt-desc field which allowed html tags. Issue was that this field only worked woth MS Outlook and I had to use alternate description field which must contain plain text format (\n could be added for new line).
I am now able to get following output now
Issue is links work best in outlook, still clickable/working in google calendar and plain text in thunderbird. Is there any way I can making them clickable in thunderbird like google calendar??