Comment 2 for bug 1502691

Hi, 4.2 is provided by the Ubuntu package base for Xenial (16.04) - I can't speak to why that would be or what may have held it back at the time, but it looks as though the upcoming new LTS (18.04, which will be Mint 19's new package base) will have 5.3 - https://launchpad.net/ubuntu/+source/rawtherapee.

This, unfortunately, happens from time to time, as a consequence of using a long-term-support base.