This app does not include System Shock's game data - it's copyrighted,
proprietary content that can't be redistributed. To play, you need a
copy of System Shock: Enhanced Edition (e.g. from gog.com).

From your Enhanced Edition install, you need its classic-game data and
sound files - the res/pc/hd/data and res/pc/cdrom/data trees merged
together (res/pc/hd's copies win the couple of filenames present in
both: intro.res, objprop.dat), and the res/pc/hd/sound tree, packed
inside the install's sshock.kpf (a zip file).

Using SideQuest (or any MTP file browser) with your Quest connected,
copy that merged data into:
  /sdcard/questshock/res/data/
  /sdcard/questshock/res/sound/

(shaders/ and this app's default soundfont are already here, extracted
automatically on first launch - only res/data/ and res/sound/ are
missing.)