Will Journal app be available for macOS?

Apple has not announced any plans to do that. We can only hope and let Apple know, that we need the Journal at the Mac as well. You may want to send feedback with a feature request. Feedback - macOS - Apple

I would prefer to use the journal on my Mac as well. It is much easier to do it on a device with a large display.

I hope so too!

I've submitted feedback requesting a MacOS version. I hope there are a lot of people requesting this. I'm quite surprised it was only released for iOS.