Windows Server Essentials 2016 Client Backup on Windows 11 Pro unusably slow

I have just upgraded one machine to Windows 11 and everything appears to be working fine (a few tweaks needed for networking printing and some software updates). For WSE2016, I had to uninstall/reinstall the Windows Server Essentials 2016 Client Connector for it to connect correctly to the server - but everything seem OK with the ability to configure the backup working fine (a useful test of proper connectivity of the client to the server).

HOWEVER, now I have started a client backup it has currently taken around 16 hours to backup to currently get to less than 40% complete. Previously the (incremental) client backups take minutes and they continue to work fine on my other machines, running Windows 10 Pro 21H2. All machines connected via Gbit wired network.

Has anyone else tested WSE2016 Client Backup on Windows 11? Have you seen the same issue?
How do we report this to Microsoft - I am reporting through Insider Feedback, but suspect the WSE2016 client may need updates, so want to make sure that the "bug" gets to the WSE2016 team as well, whilst it is still formally supported (End of Life being 11 January 2022).

The PC is an Asus ROG Maximus XI Hero (WiFi) with Intel Ethernet adapter running Intel's latest driver (26.4) so I am also waiting for Intel to release updates with specific Windows 11 support, and for the first round for updates for WIndows 11 expected on 12 October.