Hello Binu Joseph (MINDTREE LIMITED),
We got a confirmation from my internal team that this is by design. S8 and S9 are being deprecated: Azure S8 and S9 Analysis Services SKUs retiring on 31 August 2023 | Azure updates | Microsoft Azure
So, we don’t have it as an option in the Azure Portal because we are retiring that hardware offering to discourage the use of this hardware because it is very limited.
You can still switch it back to S9 using PowerShell though: Set-AzAnalysisServicesServer (Az.AnalysisServices) | Microsoft Learn
Customers should upgrade to S9v2 or move to Power BI Premium if they don’t want to pay the new S9v2 cost.
I hope this helps. Please let me know if you have any further questions.
If this answers your question, please consider accepting the answer by hitting the Accept answer and up-vote as it helps the community look for answers to similar questions.