TLDR: Update page shows "Your device is missing important security and quality fixes." for the last one week. It is still in Version 1909 Build 18363.1556.
Long story: It has been promising Feature update 2004 for quite a long time but did not really deliver. However, I had been getting regular security and quality minor updates. Around a month ago, when I started getting the end of service notifications for 1909 I tried to force updates by hitting "Check for updates" and it tried doing a huge download for 20H2. I think after a long installation process it aborted around 45% and rolled back. Tried a couple of times and the same result.
Now, I did a few methods suggested in various forums and Microsoft support sites like running update troubleshooter, a scan, running commands as administrator, setting right a few registry entries etc. I even rolled the last cumulative update for 1909 KB5003169 and it got reinstalled on the next reboot but the "Your device is missing important security and quality fixes." returned.
I am worried because I will be missing out important security updates given that 1909 has reached the end of service.
UPDATE: The error code against the update 20H2 update is given as 0xC1900101