The format to identify a user on the Ubuntu box is not obvious on the first attempt for a domain joined computer with active directory user accounts.

Normally you would use the format ssh user1@192.168.22.15 to connect. This works fine for local accounts not associated with active directory.

However, connecting to an active directory account needs a different format. You need to include the full active directory user name then add the computer address. It ends up looking strange but works. ssh aduser@jmw.blog@192.169.22.15 This connects and resolves to the AD user name on the computer. This works both with Ubuntu and with PuTTY.

Note that the active directory user must already be authenticated on the Ubuntu computer. The SSH protocol will not check authentication of a new user against active directory; it only checks the local status.