Hi @zzy!
I´ve tried the 2018.4 LTS version to make the build and it works.
I have also tried to import the package in 2019.3, make some changes, then re-do a pack to export to 2018.4 and create a new build, and it also works. So the thing is not to do the build with 2019.3 as it doesnt work.
Hope this clarify something... if you need anything else from me, please make me know.
Thanks for your help