Upgrading Safari to the latest version - how do I do this?
I have an iMac that is 9 or 10 years old. I am running macOS Catalina 10.15.7, which, according to Software Update, is the latest version of Catalina.
However, I am now getting static from some web sites (notably my bank and the Social Security Administration) that I must use the latest version of Safari in order to access their sites. This is not a matter of inconvenience - I must be able to use the online facilities as I live in a foreign country and I cannot visit branches of my bank nor can I visit US Embassies because I'm not a US citizen any longer.
Evidently, I can't update Safari independently of macOS. OK, the Tech Gods have spoken, etc.
The question now is: Do I have to buy a new computer to get macOS Sonoma (or whatever the most recent edition is, I hate the whimsical names) and concomitantly the latest version of Safari?
If not, how do I update macOS to the most recent edition?