Why cant I update from HighSierra to Catalina? (I do not want BigSur)

Why can't I update from HighSierra to Catalina?

Apple links are falsely directed to BigSur update even if I click the update for Catalina.

I do not want BigSur on my other Mac, but just to update it to Catalina.

Any advise?

Is Mac becoming like Microsoft was forcing to do updates?

I have used Mac for over 2 decades.