I would like to upgrade to iOS 14

You can download the public beta, but that would not be a good idea if it is for your only phone, because beta is short for “beta test”, meaning it is full of bugs, some of which could make your phone unusable. I’ve seen a lot of posts from people who installed, it, then asked for help to remove it.

If you are still interested—>https://beta.apple.com/sp/betaprogram/

If you have a compatible device, you can update when iOS 14 is released later this year.

That is beta software.

The stable release for everyone will be sometime in the fall

zhanna257 wrote:

Apparently some already managed to download iOS 14 and successfully using

Then they would be developers, beta testers, or they have downloaded from a hack site.