From macOS High Sierra 10.13.6 directly to Catalina?

Yep. See How to upgrade to macOS Catalina and follow instructions. It also has the direct download link for Catalina.

The very first step would be to verify that all your apps are

64 bit because Catalina does not support 32 but apps.

In addition, make sure all your apps are Catalina compatible.

Update them if updates are available to make them Catalina

compatible or purchase upgrades if necessary.

Also, if you have any third party hardware, make sure that

all of their drivers are Catalina compatible or have updates to

make them compatible.