The scenario "Last Flight".

It seems like it exists, but in my opinion, it's not very interesting to play through campaigns and scenarios in 3.1 when they were created for earlier versions.

It depends on the mod. But in general, playing 3.1 campaigns and scenarios from earlier versions is usually easier. For example, the third mission for Raileigh, in my opinion, and not just mine, is the most difficult in the fifth campaign. But with the "Nimble" skill, it will become much easier.
Although when I tried to play through the campaign in 3.1, but with new, very difficult neutral creatures, it wasn't very easy.