When the OKR model configuration for your account is set as 'Objectives are always aspirational, key results are always measurable', there is no option to update your progress "Automatically from a data source".
This is because according to the configuration, the objectives are aspirational goals hence the progress of an objective must roll up from its key results.
The integrations can be used to track the % complete progress as well, so why can't the integrations be used with such objectives?
In the given configuration, setting a metric-driven objective is not recommended. The metrics should be under the objective and ideally a balanced set of more than one, while the objective is an inspirational call to action. That's why there is no option to directly integrate with the objective.
But what about the objectives that do not have any key results or have only projects aligned to them?
You can override individual items to contribute. However, each objective is recommended to have two to three key results that are the actual measures.