This is deliberate on /e/'s part. See this post for more details
There is a gitlab issue about this, but no action from /e/. You could try adding a comment to the gitlab issue, but my personal belief is that /e/ wish to promote Bliss, and will therefore not give users a choice - e.g. in first tie setup - to easily use a different browser.
When I make unofficial and custom builds, I try to remember to re-enable Trebuchet, but sometimes I forget