Singlebox is described as 'for Mac and PC is an all-in-one messaging & emailing app - a single place for all your web services and accounts, including Discord, WhatsApp, Messenger, Slack, Telegram and many many more' and is an app in the Web Browsers category. There are eight alternatives to Singlebox for Mac, Linux, Windows, FLATHUB and Slack. The best alternative is Ferdi, which is both free and Open Source. Other great apps like Singlebox are Rambox (Freemium, Open Source), Franz (Freemium, Open Source), WebCatalog (Freemium, Open Source) and Firework (Freemium).
Franz is a free messaging app / former Emperor of Austria and combines chat & messaging services into one application. Franz currently supports Slack, WhatsApp, WeChat, HipChat and many more. You can download Franz for Mac, Windows & Linux.
WebCatalog lets you turn any web apps into desktop apps (a.k.a. site-specific browsers) with many additional features to enhance your workflows. It also protects you from cross-website trackers and preserving your privacy.
Stack is an Internet launchpad that increases the efficiency of working with the web for the average internet user by allowing simultaneous use of multiple web apps within a neatly organized working environment.
Tangram is a new kind of browser. It is designed to organize and run your Web applications. Each tab is persistent and independant. You can set multiple tabs with different accounts for the same application.