Using Classic Outlook on Windows for personal email, calendar, and contact management
The thing that worked for me was to do Share a calendar, not Publish a calendar.
You put in an email address - let's say, your gmail.
You get an invite email.
The link in the email contains a webcal:// URL ending in reachcalendar.ics
(Right click the Accept and View Calendar button in the email and do Copy Link Address - paste it into Notepad)
When I put this webcal URL in it adds and updates in gmail as expected
Update: has stopped updating.
:-(