System

Ronasara wrote:

A word of caution. Doing either of these upgrades will result in being unable to open any of your 32 bit apps, if you still have any.

That is why this is on the page I linked…

Learn more

If the installer shows a list of apps that are not optimized for your Mac, learn about 32-bit app compatibility, then choose whether to proceed with the installation.

You can upgrade to Catalina now. Big Sur once it's released.

Open in Safari, Firefox won't work.

How to upgrade to macOS Catalina - Apple Support

If you upgrade to Catalina none of your 32 bit apps will work. To find out which of your apps are 32 bit and will have to be updated, upgraded or replaced with an alternative download and run the free GO64 app. You'll be able to easily identify those apps.

A word of caution. Doing either of these upgrades will result in being unable to open any of your 32 bit apps, if you still have any.