The OpenAstronomy Azure Pipelines tox template supports running tox inside docker containers. "This was originally added to support testing against 32bit linux builds using the manylinux official docker images, so there is specific support for these images."

There does not seem to be any public repos on GitHub using the manylinux option or any of the docker_ options. However, only astrofrog/fast-histogram and astropy/astropy-healpix are using the linux32 option.