We’re using non‑persistent multi‑session VDAs provisioned through MCS with ephemeral OS disks in Azure. In the Azure portal, these ephemeral disks are shown as Standard HDD, which raised concerns given Microsoft’s announcement that Standard HDD OS disks will be retired later this year. For anyone running a similar MCS + ephemeral disk setup... Do your ephemeral OS disks also appear as Standard HDD in the Azure portal?

that's normal, the summary view for the VM should show you the Ephemeral State

Yes it does show as an ephemeral disk. If Azure identifies those as a Standard HDD, what happens when they retire that?

shrugs I am sure they will have a mapping path in the mix - maybe they will make it show something a bit nicer