Some more info here:
https://tweet.whateveritworks.org/TitterDaily/status/1674765247255654400

NEWS: Twitter's web version no longer allows users to browse without logging in. All urls redirect to the signup page.
This is believed to be a measure to make it harder for scrapers to take Twitter's data, like ChatGPT's web browsing plugin has been doing.
It is understandable that Twitter wants to protects its data from being taken for free, though this move undoubtedly reduces Twitter's reach and exposure from external links/embeds, as well as raising some privacy concerns. Hopefully a better solution can be found longer term.

This latest move by Twitter is likely linked to Elon discovering earlier this month that ChatGPT can scrape Twitter data via its web extension.
Elon previously cut off ChatGPT's access to Twitter data, and has begun a lawsuit against OpenAI/Microsoft.
OPINION: Although some of this is understandable, Twitter should atleast let users open links without signing in.
A good compromise could be letting them see a few comments and tempt them to discover more which prompts them to sign up or sign in.