My main machine is running Slackware64-current. I do most of TDE relevant development there.
Ray-V's slackbuilds are stable and work really well, occasional bugs notwithstanding, but some apps might not have slackbuilds (it's not a "package everything" approach).
I actually have a slackbuild generator script I use for building apps not in Ray-V's slackbuild collection and for development purposes. If there is interest I could publish it somewhere (probably on my Github). It is somewhat hacky but works well enough for most purposes (just not core packages, Ray-V's slackbuilds are just better).
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Philippe