How do I uninstall one update
 

Running Linux Mint Alyssa. If an update is installed through the Update Manager and for some reason decide to uninstall that particular update, how do I go about that other than using Timeshift?

You can right click on the update listed in synaptic. If synaptic is not installed,
[CODE]sudo apt install synaptic[CODE]
Then search for your app in the search box.

You can also
[CODE]sudo apt [remove or purge] some-app-you want to uninstall[CODE]

[CODE]sudo apt remove[CODE]
[CODE]sudo apt purge[CODE]
for help

Why not use timeshift? sounds like a good solution.
Otherwise, revert each update manually to its previous version. APT history can help. But this is failed to doom if you ask me.

Considering Linux Mint's update mechanism is different from that of Ubuntu/Debian, I do not recommend this.

I'm not intimately familiar with Linux Mint, but I do know that it's a Debian derivative.

You can do one of two things. You can see if you still have the *.deb of the prior version of the package on your system (try /var/cache/apt/archives) or you can use the Debian Snapshot repo to download the previous version of the package as a .deb. In either case, install the older version of the package as follows:

Warning: Do NOT use this technique for packages like libc6. You can hose your system.

Do you have a particular example of what package you're trying to downgrade, and why? Did the update cause a problem?

Some packages get installed as prerequisites to other packages. You might install chrome, and that might cause a whole list of other packages to be installed. Removing or downgrading those packages may break chrome and/or any other packages that it is a prerequisite for.

All good advise. Thanks