The events of my post happened in the last two months on Julia version 1.11.5, and this poster simply linked to a primer on PackageCompiler.jl which is the thing I said I was using in my post. It's not solved; at best there are complicated mitigations that let you control when the long compilation happens without avoiding it. If you try out Julia, you will run into the issue, and as a first-time user you won't be prepared to implement the mitigations, none of which are suitable for ad hoc usage. The sysimage only works for us because we rarely change our packages so we can build it ahead of time in GitHub Actions.