Hello @Paulh10001 

I'm afraid Hardware version is fixed on the device and could not be upgraded.  Range Extender could update firmware according to its hardware version & country version , like RE450 V1 (US) need to update V1 (US)version firmware

Thank you for being interested in TP-Link OneMesh, this requires a OneMesh compatible router and OneMesh compatible RE/ Powerline kit.And here is the Tp-Link One mesh Compatibility List :
https://www.tp-link.com/onemesh/compatibility/
If the model is not listed or marked as" Planned" that means so far there isn't  a plan to add a OneMesh on that model/ version, you may consider purchasing the version models that already support this feature.   Hope this helps.