Free open source alternative app list of Fantastical :

Itsycal

Itsycal is a tiny menu bar calendar. If you want, it will display your events as a companion to the Mac Calendar app.

FreemacOS

Others are looking for free open source alternatives of following apps:

AI & Machine Learning

Free open-source AI & machine learning tools.

Adobe Premiere Pro

Adobe Premiere Pro is a professional video editing software for film, TV, and web.

AdGuard DNS

AdGuard DNS is a DNS-based service that blocks ads, trackers, and malicious websites.

AdGuard

AdGuard is a cross-platform ad blocker that filters web content and protects privacy.

Ad Blocker

Ad Blocker is a browser tool that removes intrusive ads and pop-ups from web pages.

Acorn 7

Acorn 7 is a Mac image editor for editing photos and creating graphics.