As mentioned here

https://docs.microsoft.com/en-us/sharepoint/dev/sp-add-ins/add-in-permissions-in-sharepoint

and here

https://docs.microsoft.com/en-us/sharepoint/dev/solution-guidance/app-only-elevated-privileges-sharepoint-add-in

it ist stated, that using AppOnly Permissions is restricted for UserProfile and TaxonomyStore (whereas Taxonomystore is unclear).

However, as now CSOM supports .Net core, but only with AddIn-Model authentication, we have no possibility to use that to update UserProfiles or TaxonomyStore in an automated way in the backend using .Net Core.

At least if that documention is still correct.

Currently we have to use a service user and .Net Framework CSOM to do that tasks. But this on the other way prevents us to use new technologies for example in Azure, which is moving to .Net Core (eg. Functions support .Net Framework only in oldest v1-Version).