Upgrading OS X Yosemite to Catalina. How will it affect my Adobe CS4 software?

I have delayed upgrading my system software because I am afraid it will affect my old Adobe software. Now that I have changed my internet provider from Verizon DSL to a local Broadband, I find that the internet cuts out on me frequently. Broadband provider says that the system is operating fine on their end, but that my old OS could be the problem. I am reluctant to upgrade the OS because I am pretty sure that means I will have to start paying $52.99 per month for CS Cloud software that I use infrequently, but need for work at home.

Any suggestions?