Hi.
New Kate 5 is missing some plugins, which are commented out in cmakelists, specifically Text Filter, Mail files, File Templates, Text-to-Speech, XML Validation.
I was just wondering why and whether this is going to change in the future?
I really miss Text Filter...

I also badly miss the text filter plugin. I have used it for many years and have written numerous
filters to use with it. It was part of Kate 3.14.1 as installed with Ubuntu 14.10, but disappeared
when i upgraded to Ubuntu 15.04 (Vivid Verlet) and with it Kate 5.0.0.

How can I get text filter back?

Plugins are missing because they were not yet ported to KF5.
I miss XML Validation plugin. As I noticed, it even disappeared from docs.kde.org, but I can still find that instructions in F1 help menu and in google cache.
While looking through source code, I have noticed, that there were commented stubs for these plugins very long time ago, even before they were moved from addons/kate/CMakeLists.txt to addons/CMakeLists.txt with this commit.

Later nobody ported them and they were deleted from CMakeListx.txt with their subdirectories with this commit.