This seems to be a juliaup issue ("Juliaup configuration is locked by another process, waiting for it to unlock." · Issue #598 · JuliaLang/juliaup · GitHub), and the solution might be to run
juliaup config versionsdbupdateinterval 0
juliaup config backgroundselfupdateinterval 0
to disable checks for updates. Alternately, you may launch julia by specifying the binary path directly instead of using juliaup.