chuck I don't think this is our libc. Pretty sure that's the one being provided by Proton. You might dry a different version of the Proton runtime. Looks like you are running Path of Exile? ProtonDB suggests Proton 6.3-6: https://www.protondb.com/app/238960
If you're still having problems, this might be one of those times where going into Linux Steam Integration and disabling the Native Runtime is necessary (don't forget to restart Steam after).
joebonrichie Our build server is westmere and surprisingly no one has encountered this so far. I'm guessing your system is older than westmere.
Sandybridge is newer than Westmere and it looks like this is using a vendored libc, not ours, afaict.