Ii run Slack outside of a tab and in its app format because it's easier to navigate to using keyboard shortcuts and OS level features. That may not be enough for you, but it's plenty reason for me, and I imagine many others.
In the Chrome menu, select More Tools / Create Shortcut... and edit the title and check the Open as Window box.
In Edge, select Apps / Install this site as an app. Edge has a lot more options here than Chrome. You can pin it to the Taskbar or Start, create a desktop shortcut, and set it to auto-start. (You can do those manually with a Chrome shortcut if you know your way around the Start menu and Startup folder, but it's easier in Edge.)
I don't see a similar option in Firefox. No idea about Safari. If anyone knows about those browsers, please comment.
And having posted this comment, I am now wondering why I am still running the Slack app. I think I will try making it an Edge app!
That one of the reasons I don’t use the Google Chats PWA , when the browser misbehave, it will affact PWAs as well.
The comment I replied to described a preference for the app because of OS navigation, e.g. Alt+Tab, a separate taskbar icon, etc.
This Chrome shortcut or Edge app trick lets you combine these approaches, running the website in your browser but giving the site its own main window that you can pin to the taskbar, set to auto-run, and navigate to like a native app.
Contained within a tab Slack can only use a set amount of resources allotted by the browser.
Whereas installing the app means it can go full hog.
If the code is based on HTML/js/CSS and not Swift/Obj-C/C++ (etc) then you're really creating a web app running in a native microbrowser.
Which is very much not the same thing as writing OS and system calls directly - not least because it will be much slower.