IIRC https://addons.mozilla.org/en-US/firefox/addon/tab-groups/?s... is a replacement

Container tabs is totally different, that's about basically having multiple profiles in one window. E.g you can have the work container logged into your work email and work stuff, and your personal container logged in to your personal email and personal stuff, and they don't know about each other. Like incognito, but persistent and within the same window.

That looks really good! I'll have to try it out first, but it makes me more hopeful about Firefox's future.

Will it work after the legacy addons support is removed? If yes, how can you tell? I couldn't find any related keywords I know on the addon's page.

I didn't know of this one, is its tab management any good ? As in how do you move tabs around groups, open/duplicat/close tabs and groups ?

The 'simplified' in its name makes me doubtful it has any of the advanced features I need.

No idea, I haven't used tab groups in a year, so I've never tried the new version.

These "redone" addons that work post 57 start out pretty bare-minimum but they rapidly gain features.

I've been looking for something just like this for Chrome but haven't quite found it yet.

According to its developer it is the only of his extensions that may have a shot at surviving webextensions, though requires a rewrite and dropping of some of the useful features.

  Tab Groups has a shot. I took on this project after it was
  decided to remove the built-in Tab Groups from Firefox, as
  I thought it could be a good and fun learning experience;
  it hasn't been, if anything it's been stressful and
  time-consuming. I don't really use groups outside of my
  development profile, with my browsing habits I only find
  them useful to a point, they're helpful for my
  development/coding workflow, but I've used them maybe twice
  in my main profile during normal browsing.
  
  Its core functionality and basic workflow probably can be
  made into a WebExtension, but only after an almost complete
  rewrite of the code (with some major work done on Firefox's
  side as well!), and still stripped down of at least some of
  its features. Many of the new groups features I've wanted
  to add since the beginning are impossible though, for the
  same reason as I mentioned above: they either don't fit the
  scope of what can be allowed through WebExtensions or their
  implementation would be far too complex to do on my own.