About to upgrade Central from 1.3 to 1.4 and was upgrading system packages on Ubuntu running only ODK Central and got this screen. Does Central use grub-pc? Do you know if the "local version currently installed" is something that Central modified?
Show the differences between the versions...
What Ubuntu release are you running there? Did you do a dist-upgrade?
Ubuntu 16.04.7 LTS (GNU/Linux 4.4.0-1118-aws x86_64)
got the message that
48 packages can be updated.
2 updates are security updates.
and the above was during
sudo apt-get update
sudo apt-get upgrade
Central does not touch grub so it’s not us.
But as a maintainer of many Ubuntu installs, this is a fairly common message. I usually get it when there is some kernel upgrade.
It’s generally safer to accept the maintainer’s version. Accepting your local version only makes sense if you’d made changes you want to keep (e.g. you’ve installed a samba server and tweaked the config).
FYI, Ubuntu 16 reached end-of-life April last year. It’s time to do a dist-upgrade.
Is it recommended to use Ubuntu 18.04.6 LTS or 20.04.4 LTS?
I generally run the latest Ubuntu LTS. That's 22.04, but that just came out today and I haven't tried it at all, so in this case, I'd recommend 20.04 
To upgrade a release you'll need a do-release-upgrade. A dist-upgrade only upgrades the kernel.