I just installed iOS 11.2.1 on my iPhone 7 Plus, my daughter’s iPhone 6, and my wife’s iPhone 6.
I have an @me address tied to my iCloud account. My daughter has an @icloud account tied to her iCloud account. My wife has an @gmail account tied to her iCloud account.
I was able to invite my daughter with no problem—worked exactly as expected.
When I attempted to invite my wife, I got the familiar “not associated to an iCloud account” nonsense. Then, I went to her phone and added a “home” and invited myself to it. After that, I went back to my phone and attempted to invite her to our home. Invite sent!
I then deleted the dummy home from her phone and we’re all good.
NOTE TO ALL: make sure that the people whom you are inviting have notifications for Home ON! If not, the invite will not be delivered and you will have to cancel the invite and resend AFTER the target guest has turned on notifications for Home.
I feel sorry for all who are still stuck, and the patch is obviously not perfect (see above for what I had to do to get my wife invited), but it does seem to work in some/many cases, especially when the target guest has an @icloud account tied to their iCloud account.
Good luck all!