I think the posts in this thread show that using 5.12 would not make more sense.....Debian uses KDE Plasma 5.14. I was also surprised the Debian team picked up a non-LTS version of Plasma. Using Plasma 5.12 LTS would make more sense....
It is certainly not the newest, and for those who want the latest functions and options that plasma can offer, it will not be the best....So many kde users think So, despite love for Debian or MX and Plasma 5, have to conclude Debian 10 KDE or MX kde is not the best option on the market.
But there will be users for whom version 5.14 works fine and are happy to use it combined with the MX Tools. Remember, it's members of this community that were requesting for a KDE version.
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Technically, it would be possible to upload a newer version of KDE Plasma to the Debian 10 backports; currently that would be 5.17.5 since that’s what’s in testing. Given the number of packages involved, at least if you want to provide the full KDE package set, that would represent a considerable amount of work.
But may be in next kde of Mx we may consider using Debian stable with Plasma from Debian’s back-ports (Like neon which based on Ubuntu LTS but Plasma LTS updated)?????
Debian backports are run by Debian, not MX,
Debian Testing is the repo for the eventual Debian 11. Just because ver 5.17 is in testing repo, it does not mean back porting is automatically possible to make it compatible with Debian 10.
I believe the team did explore trying to rebuild 5.17 for MX-KDE and ran into difficulties. It's not so easy.
Currently Backports does not contain any newer version of the plasma desktop. We'll see.