Smigl
Until someone solves the problem globally (either Microsoft or Linux) :
If your machines are all on the same network, and don't go near the internet, just re-enable SMB1
OR
Get your Win10 to backup to the XP, then include the new backup with the regular XP ==> SME backup.
Kludgy, but hey....gets job done.
Remember, this is not an SME problem. It's a Microsoft v Linux issue.
Cheers
Floyd