In an RSS feed, a tweet containing only a GIF and a quote-retweet will not have a title and will thus will have no link to that tweet
The title is confusing but basically the problem is this:

User A writes a tweet. Let's call this tweet R.

User B quote-retweets tweet R and inputs only a GIF in their tweet (with no additional text). Let's call this tweet S.

In the RSS feed of User B, the entry for tweet S does not have a title, which means that entry does not have a link to the nitter website version of tweet S. (When looking at the body of the entry of tweet S, the URL of tweet R is displayed. This is expected and is not a problem.)

Looking at my feed reader's source code, I can see the URL of tweet S is in fact there, just without anything between the `<a>` and `</a>` tags. So actually, the link to tweet S is effectively invisible and unclickable.