As of 2/8/2022 at least, In Power Automate, this error -
The 'operationOptions' property is not allowed on the trigger when the workflow contains actions of type 'OpenApiConnection'
... can also happen when you have schema validation turned *on* on an HTTP Request trigger action ("When a HTTP request is received").
(Presumably, changing *any* setting on the HTTP Request trigger in PA will cause the same error message - but I have not tested this).
Make sure to turn this, and possibly any other setting, off, if you had turned them on.

Why? I don't know. If you need to do schema validation for an incoming HTTP request in Power Automate, throw in a Parse JSON action after the HTTP request with the schema you expect, instead.
Thanks,
Andrew