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Why you shouldn't use Brave Browser
(www.spacebar.news)
This is a most excellent place for technology news and articles.
In the settings under "custom add-on list". You might need to enter dev mode, which you do by tapping the Firefox logo in the about menu 5 times (you get a toast with your progress).
After that you enter the userID ND the collection name in the popup and confirm.
Details:
https://support.mozilla.org/en-US/kb/extended-add-support
And a reddit comment with a list you can use:
https://www.reddit.com/r/firefox/comments/j1ta1s/comment/g720d72/