Due to the last Steam update, if you encounter issues to launch Substance 3D Designer, you can use this work around:
Launch the Steam client with -compat-force-slr off.
We are currently searching for some solution to avoid to use this workaround.
Sorry for the inconvenience.
The Substance 3D Designer team
More info:
[url=https://9to5linux.com/new-steam-client-update-improves-native-linux-gaming-and-fixes-many-bugs]9to5linux[/url]
[url=https://steamcommunity.com/groups/SteamClientBeta/announcements/detail/4507632124224426489?snr=1_2108_9__2107]Relevant Steam release notes[/url]