Microsoft recently released notes for customers who are running on current branch 1910 , Client automatic upgrade happens immediately for all clients after you update the site to 1910.
For more information about the release notes, please refer https://docs.microsoft.com/en-us/configmgr/core/servers/deploy/install/release-notes#client-automatic-upgrade-happens-immediately-for-all-clients
Today ,Microsoft has released an update to fix for this issue and is now available in the console.
This update is applicable only to early update and globally available installations of Configuration Manager, version 1910 that are installed by using one of the following package GUIDs:
0BB82139-0DC3-4B18-B219-97FB2EFD9E56
E2F7B2F9-4828-4650-9144-5DC7956781B7
It is also applicable to the following package GUID's with the private TAP rollup, or update KB 4535819 applied:
3B4824FF-02FC-40B8-95AB-2AE986B0B63F
D237809A-6210-4209-A0E6-247543C241E4
Note: This issue is already resolved in the revised version of Configuration Manager version 1910 released on January 17, 2020. so if you haven't installed 1910 yet then the issue already taken care in the form of new build.
To verify which build is installed, add the Package GUID column to the details pane of the Updates and Servicing node in the console.
As you can see , i am running package ID D237809A-6210-4209-A0E6-247543C241E4, hence the available is available in the console .
Choose the update and click install update
This hotfix is only about 20bm in size and you can see this in configmgr easysetuppayload folder.
click Next
Click next to see the summary.
you can monitor the status from monitoring node \Monitoring\Overview\Updates and Servicing Status
Alternatively you can monitor using log cmupdate.log and ConfigMgrSetup.log
Since the update is 20mb file, the process complete in less than 10 min.
After you install this update on a primary site, pre-existing secondary sites must be manually updated. To update a secondary site in the Configuration Manager console, click Administration, click Site Configuration, click Sites, click Recover Secondary Site, and then select the secondary site. The primary site then reinstalls that secondary site by using the updated files. Configurations and settings for the secondary site are not affected by this reinstallation. The new, upgraded, and reinstalled secondary sites under that primary site automatically receive this update.
Run the following SQL Server command on the site database to check whether the update version of a secondary site matches that of its parent primary site:
select dbo.fnGetSecondarySiteCMUpdateStatus ('SiteCode_of_secondary_site')
If the value 1 is returned, the site is up-to-date, with all the hotfixes applied on its parent primary site.
If the value 0 is returned, the site has not installed all the fixes that are applied to the primary site, and you should use the Recover Secondary Site option to update the secondary site.
Reference: