To reproduce:
1. Install CentOS 7 minimal and update (sudo yum update -y)
2. Install the following packages: sudo yum install gtk3 mesa-libGLU GConf2 libpng libarchive
3. Download/curl the installer at https://beta.unity3d.com/download/6e9a27477296/UnitySetup-2018.3.0f2
4. Run the installer with: ./UnitySetup-2018.3.0f2 --unattended --components=Unity,WebGL --install-location=INSTALL-LOCATION-HERE
5. Run the installed Unity with: ./Unity -quit -batchmode -nographics -serial SERIAL-NUMBER-HERE -username USERNAME-HERE -password PASSWORD-HERE -logfile

Expected: License is activated and there are no errors.
Actual:

Output is the following:

Initiating legacy licensing moduleDisplayProgressbar: Unity license
[0214/100328:ERROR:browser_main_loop.cc(161)] Running without the SUID sandbox! See https://code.google.com/p/chromium/wiki/LinuxSUIDSandboxDevelopment for more information on developing with the sandbox on.
Cancelling DisplayDialog: Failed to activate/update license. Timeout occured while trying to update license. Please try again later or contact support@unity3d.com
This should not be called in batch mode.
(Filename: /home/builduser/buildslave/unity/build/Editor/Platform/Linux/EditorUtility.cpp Line: 257)