FWIW I am currently building a relocatable julia library, wrapped into a python module (but can be used as an executable or C library aswell). See here and also the discussion in Creating fully self-contained and pre-compiled library. However, it is true that this has similar amounts of relocatability as PackageCompiler.jl but comes with the extra guarantee that no further code will be compiled at runtime. My goal is currently just to support x86 Linux usecases with glibc>=2.30. This is going well (after quite some effort). Do you need relocatability also to other architectures? In that case it may be possible to make separate builds for x86 and arm and different OSes and then handle somehow that the target system downloads the correct version (common usecase for package managers). In theory I believe this will be no problem.
For an example of the “relocatability” you can check this github workflow file which first builds the library on one machine and then tries to run it on another machine.