so - after playing around here's a list of pre-requirements to resolve all missing dependencies:

steam
lib32-fontconfig
lib32-libpulse
lib32-openal
lib32-libtiff4
lib32-libcups
lib32-libsm
lib32-libudev0-shim
lib32-gstreamer0.10-base
lib32-gperftools

I use YAY but any other AUR aware manager should be able to figure out the stuff

! be aware !
as there's no easy way to get python2 you will build it from source to get lib32-gstreamer compiled from source (unless someone knows an easier way to avoid building python2 from source which would speed up the process by a mile - maybe some repo providing it pre-built)

as already mentioned elsewhere: the current linux build is quite outdated - and has quite a lot of issues and out-of-date dependencies - do yourself a favor: don't even try it yourself - use proton and run the windows version - it will save a you lot of time and it runs better and has less issues

! important !
you also have to re-wire the provided libtcmalloc_minimal.so.4 from <bm>/bin to /usr/lib32
there's a known bug about native linux source games come with a bad version of that file - that's what lib32-gperftools is for: it provides a current working version
the linux way is to either rename or delete the file the game comes with and symlink the system lib

if you can figure out the packages and its dependencies on your distro the above should work for you
to make sure you found all put this into a script (nothin harmful - just a cut down version of the bms.sh launcher script to call LDD on all .SO with the correct path set) and grep for "not found" - if it returns empty you have satisfied all dependencies:

#!/bin/bash
GAMEROOT=$(cd "${0%/*}" && echo $PWD)
export QT_ROOT_SUFFIX_DIR="${GAMEROOT}"/bin/thirdparty/qt-5.9.x-linux-x86-g++-32
export LD_LIBRARY_PATH="${QT_ROOT_SUFFIX_DIR}"/lib:"${GAMEROOT}"/bin:$LD_LIBRARY_PATH
for i in $(find . -name "*.so")
do
ldd $i
done