i decided to take one last stab and to get very methodical about the issue i've been having with regard to hydrogen (and other programs) requiring sudo to run. here's what happened.
i did a fresh install of ubuntu studio. rebooted. i ran hydrogen. aok.
i added kx repositories. rebooted. i ran hydrogen. aok.
i installed catia. rebooted. i ran hydrogen. aok.
i installed cadence. rebooted. i ran hydrogen. it flashed its splash briefly then closed. required sudo to run.
i purged cadence. rebooted. i ran hydrogen. aok.
that's all i got. hope it's useful.
BabaG
final report on oddball permissions issue
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