@Kin Yung Welcome to Microsoft Q&A Forum, Thank you for posting your query here!
There’s no option to disable SMB2.1 from customer
if you disable SMB2, SMB3 also gets disabled (Usually we won't disable SMB2) but by default it will use the latest one i.e. SMB3 only
Feel free to leverage anffeedback@microsoft.com for this scenario.
Additional information How to detect, enable and disable SMBv1, SMBv2, and SMBv3 in Windows | Microsoft Learn
Please let us know if you have any further queries. I’m happy to assist you further.
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