As you probably know, Google will withdraw password-only access for 3rd party applications since end of May and only OAuth2 or application passwords may be used.
I have multiple calendars in my Google account and I'm currently using them in Evolution as "CalDAV" type calendars. However, this method uses exactly what Google is about to withdraw - password login. I don't want to turn on 2FA on my account (to be able to use app passwords) for various reasons, so I wanted to try OAuth2. I was able to successfully configure first calendar as "Google" type calendar in Evolution (using more or less the procedure specified in this answer), but when I try to add more calendars (by repeating these steps), after clicking on the "Default user calendar" button, instead of getting a calendar list, I get a message "Data source does not support OAuth 2.0 authentication". Even when I try to use a different Google account, I get the same message.
Can there be only one "Google" type calendar defined in Evolution? If not, how to define additional calendars?
I'm using Ubuntu 20.04, Evolution 3.36.5-0ubuntu1.
Answering myself: it is possible to define multiple Google calendars, but when defining an additional calendar, you must do it in two steps.
First, define the calendar without clicking the button that changes calendars (ie. leaving the default calendar). Click "OK" and the calendar is saved.
Then right-click the just defined calendar in the calendar list and select "Preferences" from the menu. Now you can click on that button and change the default calendar to the one you want.