Hello
This morning when I started my computer Firefox (Firefox version 66.0.3) had disabled the following privacy extensions:
(a) HTTPS Everywhere {EFF Technologists}, (b) Privacy Badger {EFF Technologists}, (c) uBlock Origin {Raymond Hill}.
and the following productivity extensions:
(i) Zotero Connector {www.zotero.org}, (ii) Unpaywall {Impactstory team} [used together with Zotero].
I am now using Brave (thanks to @Wimpy for making the discovery and installation so easy {it is in the Internet section of the Software Boutique}).
I installed the Zotero Connector for Chrome and it seems to work.