I recently tried setting Apple Business Manager for our ≈20 people SME. The first step was "Domain Lock/Capture" which takes over all Apple accounts for a specific domain. I've never had a worse experience from Apple. The process is buggy, filled with foot-guns and dead ends. It expects huge amounts of work from users who have had their account for more than a few weeks and are expected to remove a lot of their perso…
The domain lock process was an absolute fiasco at our company. I think this could work if you did this at the time your company launched, but the moment you have employees who have Apple IDs tied to their work email that aren't from the Business Essentials system you are stuck in an impossible-to-mange place. There are several cheap MDM solutions for Apple devices that I would rather pay for than be dependent on this…
I had the same thing happen but with Microsoft. A friend and I had started a small consulting business and were using Google Workspace, but I needed a Microsoft account to interact with a client. I made one with my business email. None of us knew any better, but I couldn’t connect with our client’s Microsoft setup because it was a personal account. So I went to set up a business account. It was a whole fiasco and the only way I could really fix it was create an alias and use that for Microsoft.