The following packages have been kept back: python3-update-manager snapd ubuntu-advantage-tools ubuntu-pro-client ubuntu-pro-client-l10n update-manager-core0 upgraded, 0 newly installed, 0 to remove and 6 not upgraded.

https://crmn.tistory.com/m/161

[리눅스] The following packages have been kept back 원인과 해결 방법