[ducttape45]

I tried Spectacle and it didn’t work. KMail, same thing. I’ll stick with Shutter for now, and I’ll give Claws Mail a glance.

[Pollard]

That's the tricky thing about linux. Most of these programs are made with a specific desktop, desktop rendering engine or linux version but it's not always clear which one and in general, they're "supposed" to be compatible. The independent ones you find on the web, such as Claws Mail that have multiple linux downloads, Debian, Ubuntu etc, tend to work on most anything. If there's no specific Ubuntu version, the Debian version will usually work too as Ubuntu is based on Debian.

This is just the Ubuntu Family

One thing I will say though, you may be aware, even with the program/desktop compatibility issue, your home folder can be backed up and then you can install any other ubuntu flavor and restore the backup. Home is all your docs, plus config files which windows keeps in a bunch of different places. Any program your new ubuntu flavor can run, will be restored completely. I've been dragging my thunderbird profile across 4-5 different flavors of ubuntu and when I open thunderbird on the new setup, it looks just like it did before the swap. All accounts are there, all mail is there. All those config files are hidden files. The file name starts with a dot/period which tells the system they're hidden files. In your file manager, you should have a menu item to Show Hidden Files. Tick that and you'll see them.