In case anyone else is having the same issues, I believe I've found the answer. Microsoft 365 DNS can be managed via Microsoft Graph. Here's a link to the documentation: https://learn.microsoft.com/en-us/graph/api/resources/domain?view=graph-rest-1.0
Microsoft 365 DNS API?
Whereas Azure is making some progress toward providing a DNS management API, Microsoft 365 seems to be lacking anything like it. Is it just my inability to find it, or is such a thing simply not available? Alternatively, is there any way to use the Azure API to manage Microsoft 365 DNS installations?
I manage a few machines that use DHCP, and occasionally change addresses. I realize there is caching and lag time, but being able to run a service that automatically updates IP addresses in the DNS for them would be VERY helpful. I'm tired of walking people through finding their IP addresses, regardless of how easy that has become, or of having to look the machines up in some other place.