Free open source alternative app list of Bartender :

Hidden Bar

Hidden Bar lets you hide menu bar items to give your Mac a cleaner look.

FreemacOS

uTools

What is uTools? uTools is a new generation of efficiency tool platform, free combination of plug-in applications, to create your own tool set.

FreeWindowsmacOSLinux

Dozer

Hide menu bar icons to give your Mac a cleaner look.

FreemacOS

Raycast

Raycast lets you control your tools with a few keystrokes. It's designed to keep you focused.

FreemiummacOS

Vanilla

Hide menu bar icons on your Mac.

FreemiummacOS

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

Ad Blocker

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

AdGuard DNS

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

Adobe Premiere Pro

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

AI & Machine Learning

Free open-source AI & machine learning tools.

Acorn 7

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

AdGuard

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