Thank you for your reply.
Unfortunately, this Chrome extension is not available for Chromebook, so it is impossible to use. Furthermore, it appears that this extension does not work if the Kaspersky program cannot be installed.
I have the most confidence in the Kaspersky brand to secure my computers, but as long as the Android app for Chromebook doesn't exist, neither the antivirus, nor the password manager, nor the VPN will work.
So I will take out a subscription from another brand for another year and hope that Kaspersky will still release it for Chromebook/Chromebox.