I am also experiencing the same issue since iOS 12.1. It is currently August 24, 2021 and I am on iOS 14.7.1 and my Mac is on 11.5.1. It is clearly an iCloud account issue. I was given the customer profile to for the Clear HomeKit data menu on device and it did not work. I am tired off waiting 30 minutes as suggested by support for logs.
We need more eyes on the issue. I want to purchase HomePods but I wouldn’t be able to set them up without a working Home app.
I don’t know why the HomeKit data can’t be purged from the database on Apple’s side.