currently tbselenium does

# TB can't find bundled "fonts" if we don't switch to tbb_browser_dir
chdir(self.tbb_browser_dir)

which requires a writable tbb_browser_dir
for .cache/ and .tor project/

but this should also work with a read-only system-wide installation of torbrowser
and it should be possible to use a workdir in tmpfs

TB can't find bundled "fonts" if we don't switch to tbb_browser_dir

works for me

but my actual issue is

profile missing: your tor browser profile cannot be loaded. it may be missing or inaccessible.

which is caused by one of

sudo chown 0:0 "tbb_path/Browser/.cache/"
sudo chown 0:0 "tbb_path/Browser/.tor project/"

... but a different workdir does not fix that issue

i would need a read-only tbb_browser_dir = "tbb_path/Browser/"
and separate paths for .cache/ and .tor project/