As of July 4th 2023, Old TweetDeck has been unplugged, Preview is the way and will require a Verification. Meaning Better TweetDeck is obsolete and will not work anymore.
Thank you to everyone who used it, contributed to it, and supported the project over the years, whether it was by reporting bugs, suggesting features, or donating to the project. It truly has been a wild 9 years and I'm glad I could help so many people with my "little" project. I wish it didn't end so suddenly but it is what it is.
So long and thanks for all the fish!
EDIT, July 8th 2023: it seems Old TweetDeck is accessible again? I fully expect it to be an accident, I re-enabled the extensions on their respective stores but don't get your hopes up.
— Damien (@Eramdam)
Better TweetDeck was available on https://addons.opera.com, but the Opera add-ons team's review times have been very complicated to deal with, so the Opera version always was days if not weeks late compared to the Chrome/Firefox one.
Fortunately, there's a "better" way. It's a workaround, it's not ideal, but at least you'll get updates at the same time as Chrome and Firefox users!
Follow those steps:
Feek free to reach out on Twitter @BetterTDeck if you run into any issues.