Dropbox, need advice when I get a new Mac.

Ziatron wrote:

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Maybe I'm unusual, some people can just name their home folder “BobsMac” and use it forever. I don't see how I can do that.

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The usual option is to do the following with the old Mac after migrating and then set it up as new for the next user. Then there is no need to change the name on the new Mac. What to do before you sell, give away, trade in, or recycle your Mac - Apple Support

I think most people give the macOS user accounts names associated or reflecting the actual person such as "Steve Jobs", "stevej", or "hwtech", or maybe "ziatron". These types macOS names don't need to be changed when moving to another system.

Keep in mind you can give your computer an actual custom name independent of the macOS user name, so if you want to find your specific computer on the local network, then you can give the computer its own name such as "macmini2018", etc. while still having a macOS login user account named "ziatron".

I think you are focused on the wrong issue here.

https://xyproblem.info/

Ziatron wrote:

Thinking, perhaps I was an "oddball" I decided to ask artificial intelligence. (Something I'm not really a fan of.)

AI: "People change their Mac's home folder name on a new machine to avoid naming conflicts with old backups or network devices, to align the home folder name with a preferred user account name or a specific device name (like "2019 MacPro"), and for better identification of backups and network shares. Although some users may do this for privacy or cosmetic reasons, the primary motivations are organizational and functional, ensuring smooth operations when using multiple Macs or transferring data."

Note that the AI didn't say this was something that many people do.

And of course, we all know how much to trust AIs.

But you're "giving it away" and should be set up according to that Apple document so the new owner can have their own email, messages and iCloud account.