Trying to upgrade my macOS. Currently have High Sierra

I tried upgrading to the newest macOS Big Sur. But once I downloaded it I realized how much space it would take to download. With that being said I tried to free up space but its still almost impossible to download. So my problem is now every time I try to find a newer macOS system on the app store it wont allow me. I searched "macOS Catalina" and nothing I'm looking for comes up. So I found different websites that said they have the link to the app store. However, when i click the link it goes to app store but says what I'm looking for isn't available in the U.S.

I'm upgrading because several programs from Adobe aren't compatible.

Help Please!