DISCLAIMER: I am not Librem 5 develper
I have tried to help somebody else demanding andbox in the other thread when I have seen that he tries to run x86 Docker images to build android system image on the phone.
You do not need to build actual andbox binary, it is provided by CI build at Purims gitlab. Look for latest pipeline package-pureos-byzantium:arm64 artifact, download it expand and you have the required deb. But you need Andoid system image.
At the end I have managed to build image from android sources by scripts provided in the Purism project fork package-pureos-byzantium:arm64 (#364593) · Jobs · Librem5 / debs / anbox · GitLab . But actual andbox is easy to build. Problem is matching Android image. I have managed to build it after some hacks to the build process which has to be run on host GNU/Linux x86. May system has too little memory that I have problems but next changes helped me.
Resulting image works in the respect that it is able to run all ART and Dalvik machinery and run included calculator and even F-Droid and probably even install some application. But at least my built is far from state that it can be reliably used and it is based on old Android runtime. May it Wandroid can be in the better shape one day.
It would be great if @dos can report his level of the success, may it be it is breakage of my build. It would help to inform others why build Android root filesystem image is not provided. Is it licensing, problem to keep too much data to fulfill source availability or what are other reason why Android image is not made available? Its build takes really long at least on my not so dated but standard hardware.