Adblock - ? Where is it available? I don't see it here.

At AMO you can scroll to the bottom of the page to Version Information and then hit the See complete version history hyperlink to get all the older versions of an extension. Install the older version and make sure you disable updates for that particular extension.

Adblock   should not be confused with   Adblock Plus:

https://en.wikipedia.org/wiki/Adblock_Plus

The developer of Adblock,   Michael Gundlach,   claims to have been inspired by the Adblock Plus extension for   Firefox.
Adblock ceased development in 2004 and was sold to an &nbspunknown  buyer.

Guys - I used adblock for ages https://getadblock.com/

It's not on AMO but was time that was. Now only for Chrome, Safari etc.

After second though, I think I had similar problem couple years ago and someone told to change setting on firefox to allow not verified addons to run. Any hint how to do this?

If adblock is not on AMO it will be for a reason. Possibly it does not comply with AMO's rules, or maybe it was that they felt it not worth competing with AdBlockPlus ( ABP ) as explained in this

• Why did AdBlock stop supporting Firefox? https://help.getadblock.com/support/solutions/articles/6000095247

As you do not like ABP why not try one of the alternatives as listed in the-edmeister's post

• Maybe consider the AMO featured
  uBlock Origin 1.9.0 https://addons.mozilla.org/firefox/addon/ublock-origin :
  Finally, an efficient blocker. Easy on CPU and memory.

I do now tend to use that one myself, and can confirm it blocks YouTube adds on its default settings. That appears to be the main point of asking this question sensor1111 said

... but it worked nicely anyway cutting off any ads, including youtube). And now thanks to nasty update I have to watch this spammy stuff.

I'm surprised but uBlock seems to does its job properly.

So, I'll stick to ff little longer  ;)

Glad to hear that, and thanks for reporting back.