Barely provides any functionality. There are a lot of APIS usable at the moment that are not being tackled. I don't know how many users really did use TMP for it's session manager capabilities but it seems the devs are focusing too much on that now and not providing other useful features that were and still are possible to translate to web extensions since the day quantum was released.

1. I can open links in a new tab just by clicking on them
2. I can have a list of tabs I have closed
3. It will remember what tabs were open when I last closed FF every time I close FF

I like some of the other things about it but those are the 3 most important.

Leider nur in englisch und deshalb für mich nicht zu gebrauchen.
Habe versucht, durch "ergoogeln" die erforderlichen Einstellungen in about:config zu ändern. Für mich ohne Erfolg.
Ich warte, bis es auf deutsch kommt und mehr Funktionen beinhaltet. Wenn es "idiotensicher" und bestens funtioniert wie das alte TabMixPlus, bin ich dabei und werde auch dafür gerne zahlen / spenden!
2 Sterne gibt es von mir wegen der guten Absicht.
Viel Erfolg!
Michael

There are so many different features in the versions before firefox quantum webextensions, which were nice to use, at some point important to have.
I love it and would like to have it back to the new firefox, therefore I also encourage a donation.
All the best for onemen!

Well, stares are actually for the purpose of this extension and to encouragement of the developer(s). Also for expressing the need of it. Anyway, after installing it, the middle click opening in a new tab of links did not work, so I had to disable it until further version. Thank you onemen!
BTW, I couldn't register on http://tabmixplus.org due to reCAPTCHA v1 being retired. Please fix it!

A good addition, but not all functions work.

I consider this to be an essential add-on. It greatly improves my Firefox experience.

I have donated when the developer ask to help him to move to the new extension engine.
Until today, I do not see any progress in the development and only complaints from the developer.
Meanwhile I found some extensions that can partially replace the old and good TAB MIX PLUS:
Focus On Left Tab After Closing
Open Tabs Next to Current
Manually change configuration to allow always open new tab from address bar:
about:config -> browser.urlbar.openintab -> true

That`s all.

今後に期待を込めて

extraño la vieja extension .. ojala vuelvan