Twitter has disabled users from retweeting, replying or liking tweets that contain a link to Substack. Users suspect it's because Substack is preparing its own microblogging service to rival Twitter. https://www.pcmag.com/news/twitter-disables-retweets-likes-on-posts-with-substack-links
Twitter Disables Retweets, Likes on Posts With Substack Links

The apparent blocking occurs just a few days after Substack announced Notes, a Twitter-like service that lets writers post short-form content.

PCMAG
@PCMag After laying off so many from Twitter, it’s only a matter of time before these callously cast-off employees band together and put together competing products. Twitter is still holding due to its early entry into the market and current users, but that may change. In addition to my own Social Media work, I am actively encouraging companies I work with to begin using Mastadon and other competing services. I doubt I’m alone with that.