What are integrations statuses within app settings?
Can you just turn them off there?

all integrations are disconected .But the games and all their covers are still appearing

Hello,

Just uninstall normally from Control Panel. Then make sure the installation folder is gone:
C:\Program Files (x86)\GOG Galaxy
C:\Program Files\GOG Galaxy <== on 32-bit Windows

Make sure GOG Galaxy is not running in the system tray (that little corner of the taskbar).

Then move the following folders somewhere else, like a folder on the desktop. The easiest way to get to them is to paste the location into the File Explorer address bar. That way, you don't need to fiddle with showing system/hidden folders.
%LocalAppData%\GOG.com\Galaxy
C:\ProgramData\GOG.com\Galaxy

Additionally, if you took screenshots, you'll find them in
<Your Documents folder>\GOG Galaxy

There will be some cruft left in the registry, but it's unlikely to affect anything. It's more of a bother and a risk to try to delete it.

Ok, I've solved it. I just synchronized with each of the integrations I had and deleted them so that they disappeared.

Here is a question...

My hard drive was packed, so I buy 2 new ones so I can game again...

But GoG wants to install itself on my OLD hard drive, which is freaking full, and it will not give me the option to install on my gaming drive.

How do I fix this crap?

Sorry for the necro but this is simply unacceptable.
Removed with Revo Uninstaller, checked for and deleted hidden leftovers using Everything, killed background process.
Reinstalled... hey-presto, all games from other services are right back in the database.
Used Procmon to trace file activity... the only database in use is in C:\ProgramData, which was *definitely* deleted before reinstall.
There are two distasteful scenarios here:

1) The database is being stored locally somewhere where a user with a high level of Windows expertise (plus decades of experience and decent tools) can't find it
2) Even worse: they're storing that data online without express end-user permission, and no obvious way to remove it.

On top of all that, I can't even connect to 3rd party services to do the "sync and disconnect" dance - they all time out or throw errors of some kind.

Junk - deleted with prejudice.

I highly recommend Playnite instead