In case someone with the same problem stumbles across this thread, since things did not really move here I reposted my problem over at the julia forum, and someone there gave me the hint that fixed it.
Apparently the binaries from the snap store are incapable of hosting a proper LanguageServer instance. I purged my snap store julia install and reinstalled everything via juliaup, now julials runs fine. The reason for this behavior is beyond me, but now it works , I guess… 