Error - operation timeout. An all versions from 2017 to 2018.2.12 (except 5.6.6 - there’s no pack manager).
Error start from any Windows 10 upgrade, this year. And today after Visual Studio Community 2017 reinstalling.
After some days (without any my efforts) unity may to work.
May be to make a button for no use package manager, and use old package system from 5.6.6 ?
And why package manager tried to link with server in offline mode ???
After some pc rebooting it’s again work.