@kenneho This is, of course, one of the reasons that governance should come first when you implement SharePoint Online! Naming collisions are inevitable if you don't plan! If you are not ready to build your intranet when you deploy, make a land grab for critical function names by creating communication sites for things like HR, Payroll, Benefits, IT, Finance, Legal, etc. This is what I do most often when I work with clients. Microsoft IT did it too.
But, when the ship has already sailed, you need to come up with another strategy. In some cases, we have worked with the site owner to "take back the name" by migrating their team content to a new URL (usually, the culprit is a team site created for a very small number of people so the impact is small), fully deleting the original site, and then re-using the URL for the intranet communication site. In other cases, we have had to come up with other URLs - different abbreviations, such as InformationTechnology or InfoTech or ITDept instead of IT. You could also use a prefix for the URL as you suggest, which could help users quickly identify whether a site is "official." This approach will be hard to enforce if you allow self-service site creation. If you don't allow users to create intranet sites on their own, you may not need this type of naming convention because you will have more control over the site names.
