I'm not quite sure what the context of your question is, but yes, you can disconnect the Dynamics 365 integration under Settings > Integrations > Connected Apps > Actions > Uninstall.
This would remove the integration entirely and the two systems would not be connected anymore.
I'm not clear which Dynamics 365 URLs you're referring to. Out of the box, HubSpot is not integrated with Dynamics 365. If it was integrated by someone, you can always remove the integration.
Best regards!
Karsten Köhler HubSpot Freelancer | RevOps & CRM Consultant | Community Hall of Famer
Thanks Karsten, my query was more around how to prevent users from connecting to Dynamics 365 in the first instance, but it looks like I was looking at this the wrong way (essentially ignore Hubspot and to block directly via the O365 tenant instead)
I guess in order for that to work we would need 1 x main Hubspot account where we can see other users. The issue we have is users must be signing up for their own 'Free Accounts' / 'Paid for Subscriptions' etc, so no control over that - yours would certainly be the accepted solution if that were the case though so will mark as such.