This was a poorly thought through change.
A binary on/off change should have been more proactively communicated and with far greater advance notice. Further, a binary on/off change should have had a transition period.
For example: Upon rollout, there might have been no change for existing customers. However, existing customers might have been given option to elect the feature. After six months, the feature might then have become manadatory for all. This would have allowed customers to test the change and provide needed feedback to Hubspot.
At the moment, our integrations are broken. It appears no thought was given to the use case of programmatic / API-driven download of files from Hubspot. No documented means of authentication allows for programmatic download.
Prior to changing existing functionality, community feedback should be solicited. Had feedback been solicited, the full set of use cases to be supported might have been appreciated prior to implementing such a change.
First, do no harm.