kc9udx
It looks like (mentioning kdm) you use KDE 4 which last release was 10 years ago and maintainance release ended in 2017.
At the time Linux developed software was more Unix-ish.
I don't mind KDE4 but I think I can add "maintained" to every sentence of my previous post.
I think it is important.
For you point on xbattbar (based on the deprecated apmd instead of envsys).
Enters in the case of having to tinker to make it work which is not the point of fully fledged desktop (and having to tinker enters in the case of having to manually configure a WM. Some people might like it, but not everyone, I myself prefer a nice out of the box experience to put my energy on the work I am actually doing with my computer)
Of course you can make some things work by tinkering, that is beside my point.
Because my point is about integration and polishing.
And I am not speaking only about a battery indicator but also integrations in DE settings menu, power management settings.
Regarding e26/e27 BSD licensed and very efficient on slow systems makes it a very good option indeed @Jay
This could be a nice DE to focus effort for a nice experience.