Hi,
Hope everything is going well.
Do you mean you have enabled the option "Upgrade all clients in the hierarchy using the production client" in the Site's Hierarchy Settings and would like to keep old devices with old SCCM client agent? If yes, we can exclude these specified clients from upgrade, just simply create an Exclusion collection for the old devices and select the Exclusion collection you want to exclude. If I have misunderstood anything, please feel free to let me know.
After clients in the excluded collection update policy, they don't automatically install client updates. Excluded clients still download and run Ccmsetup, but don't upgrade.
Feel free to contact me if you have any concerns/queries.
Best regards,
Simon
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