Tab Unloader working just fine with all previous versions of Firefox up to 118 (on Arch Linux).
Usefull settings and default settings, ie: time to auto-unload; visually shows which tabs are un/loaded; don't unload tab that's playing Audio...
Also works fine with Tree Style Tab.

Before opening Firefox, is there some way to tell Firefox to tell "Tab Unloader" to open all tabs unloaded?

Still works. I actually use this only for the option to load a whole bookmark folder unloaded.
Would be great if there were shortcuts like ALT + Click on a link to open it in the background. Context menu item to open link in background unloaded also lacks a keyboard shortcut.

More useful than Auto Tab Discard for me, because Tab Unloader correctly counts the time before automatic tab unloading from the moment the tab was last active / in the foreground before the user switched to a different tab. Auto Tab Discard, in my testing, counts the time since the tab was first opened or last loaded back from the unloaded state, which is quite inconvenient.

Has some issues with unloaded tabs where either it or Firefox "loses" the URL belonging to the tab so the tab can never be reloaded.

Seems to happen between 1/2 and 3/4 of my unloaded tabs (Honestly the ability to reload a tab happens very infrequently, generally an unloaded tab is gone forever) so makes it a non-functional add-on for me

For me the best extension of its kind. It has all the features I need, but without any bloat. Simple and clear options dialog. An option to "bypass the cache on restore", like the old "Auto Unload Tab" extension (pre-Quantum), would be really nice. At the moment I use the extension "Update Discarded Tab On Select" for this.

There are options to "unload this tab" "unload other tabs" etc, but no reload, so I have no idea how to get back the tabs. The UI is not handy at all. I will use another addon of the same kind with a better UI,, like a tabs list for instance, or even a categorization or tagging of several tabs lists.

Doesn't automatically reload tabs.

Some of my Bookmarks now have the discarded favicon permanently. I tried to remove, and re-add the Bookmarks, but it continues to display the faded favicons with the dot. That's annoying and needs to be fixed

He estado haciendo pruebas y ahora mismo funciona mejor que UnloadTabs, además tiene más opciones y un botón para no tener que dar clic derecho sobre las pestañas cada vez que quieras descargarlas.

The Good:
- seems to be doing its job
(though FF always still manages to use many 100's of MB and multiple instances of FF
for - I think - installed add-ons, Gmail and YT etc...but prob. Mozilla's fault)
- good extra features,
like only whitelist a particular tab or its whole domain name

The Bad:
- Youtube tabs that are reloaded,
are loading the mobile ("m.youtube[...]") version.
Really annoying!

The Ugly:
- nothing important really.
Maybe the icon. On/off button prob. not the best choice.

This was the lifesaver for my laptop with only 2GB ram. I switched to "Auto Tab Discard" because it has an "... only if number of inactive tabs exceeds [ ]" option. Tab Unlader has the better ui and the better icon though, so I hope competion will bring further improvements. More memory-awareness would be nice, i.e. discard tabs if FF memory consumption exceeds [ ].

Thank you Afnan Khan, and good people at Mozilla.
I have not tested this extension yet because I still mainly use a version older than FF57("the Great Regression"), but give it 5 for encouragement. Every user of FF that uses more than 10 tabs in a session, needs an "auto unload tabs" functionality, like we need air.
After I have searched(2018) and read about/viewed screen shots (videos), of extensions that are able to unload(auto) tabs, I find this one to be the closest with the extension:"Auto Unload Tab by def00111" which does not work on FF after v56, but does a superb job on FF before 57, of unloading(auto too) tabs from multiple groups without using much CPU.
Hopefully Afnan Khan did not quit maintaining(or improving) this much needed add-on.
About the loosing of favicons of tabs it seems to be a bug of Firefox ("Most notably, tabs may loose their icons or display as loading. Fixing that is Mozillas job")...see more here: https://bugzilla.mozilla.org/show_bug.cgi?id=1450382
https://bugzilla.mozilla.org/show_bug.cgi?id=1450371

It changes favicons in bookmark to a blank icon with a yellow dot. And the worst is it can't rollback to the original one, force refresh don't work.

Does what it says on the tin. Seems to be the only unloading extension out there that does it on a timer.
Would like an option to disable the recently-added favicon replacing though - the pink blotches are unsightly and, for those who already have styling set up around unloaded tabs, unnecessary. The extension also fails to retrieve favicons of unloaded tabs after a browser restart / session restore, so you end up with a bunch of "default" icons with pink circles on them.
Would also be nice if it integrated with Tree Style Tab, so its menu options show up on the side tabs as well.