I'm glad that you were able to resolve your issue and thank you for posting your solution so that others experiencing the same thing can easily reference this! Since the Microsoft Q&A community has a policy that "The question author cannot accept their own answer. They can only accept answers by others ", I'll repost your solution in case you'd like to "Accept " the answer.
Issue:
You received the error, "This operation target is not yet supported" when trying to create a function in Powershell to edit a set of parameters. When updating the parameters, you were unable to isolate which parameters were triggering the error.
Solution:
You figured out that the issue was caused by these parameters: deviceEnrollmentLimit, birthday, preferredLanguage, preferredName
Certain properties can only be retrieved for individual users and not for a collection of users. https://github.com/microsoftgraph/microsoft-graph-docs/issues/381
If I missed anything please let me know and I'd be happy to add it to my answer, or feel free to comment below with any additional information. Thank you again for your time and patience throughout this issue.
Please remember to "Accept Answer" if the answer accurately summarized the solution, so that others in the community facing similar issues can easily find the solution.