The best alternatives to Hacker Tab are Twitter, Kamran Ahmed, and KnowledgeOS Beta. If these 3 options don't work for you, we've listed a few more alternatives below.
Pennywise is a multiplatform desktop application that allows you to open anything in a small floating window that always stays on top of the other applications all the time, allowing you to multitask with ease. No need to keep struggling with alt + tab, use pennywise and have your work in front of you all the time.
KnowledgeOS is Marie Kondo for your favorite browser. Supercharge your browser with powerful organization and interaction. Work faster, work smarter. Easily manage all your work and tabs contextually. USE FOR FREE and STORE YOUR DATA ON YOUR DEVICE.