gambarot wrote:
I need to know when Catalina will stop to be supported since I am using a Mac Book Air 2012 and I can only purchase a second-hand one since I cannot afford a new one.
The final official release of macOS Catalina was v. 10.15.7 on July 22, 2022. Most analysts & users consider that to have been the "end of life" date even though Apple does not publish an end-of-life schedule.
The last security update for Catalina was Security Update 2022-005 also in July 2022. The last Safari update for Catalina was Safari 15.6.1 issued in August 2022. To my knowledge there have been no subsequent updates.
One would conclude that Catalina has stopped being supported. But that does not mean that it is unusable or unsecure. If you have kept your apps up to date (to the extent they remain supported by their vendors), use reasonable security & privacy measures and are cautious in your use of the internet you should be fine for years to come.