@russurquhart1 I'm a little mystified by the exchanges in this thread...
I'm running Catalina on a late-2012 Mac mini, and am using Vivaldi 6.7.3329.17 / Chrome 124.0.6367.90 — the latest Stable. Without problems! (I also use the Snapshots.) The last I heard, Catalina will be supported to or through October...
Rather than trying various older versions, I'd recommend you use the latest! Enjoy! 🙂
EDIT: One further tip — for its first opening, left-click on the V icon in the Applications folder and select Open. Then you should see a two-choice dialog; choose Open...
(This dialog warns of an app downloaded from the internet — like you didn't know that! 🙂 )