Omg you just described slackware. Join us!

I would recommend void, alpine (kde plasma auto installer may still be broken for some users, works for me tho, also musl so if you need appimages or some very specific applications don't use it.), alpaquita (much stable alpine with glibc if you need appimages), slackware (current only, it is stable rolling, and their point release features very old kernel and packages so I wouldn't recommend it, paldo (stable rolling, gnome by default but plasma installable.), gentoo (if you have time to compile, why not it as stable as rolling can get without it being openSUSE), openSUSE (easiest rpm based (Oracle fork) but still IBM code nonetheless)

Slackware current.

Debian as others are saying is a great choice

But I'll still shill arch, I've literally never encountered a problem with it other than my first time installing manually being a learning experience. Not sure if it counts as a DIY distro bc you can definitely install with a script

• Siduction
• openSUSE

Same recommendation as usual from me :) pepparmint OS , Debian base extra on top

Seems that Slackware is what you are looking for.

An immutable distro with a heavily customized KDE desktop is Nitrux. Check it out at nxos.org