Ubuntu 20.04.3 went to sleep, then crashed

[Robert Pearson]

Opening in existing browser session.
[10305:10305:0100/000000.804354:ERROR:sandbox_linux.cc(374)] InitializeSandbox() called with multiple threads in process gpu-process.

Left computer. Later when I tried to wake it up, no video signal from onboard graphics. No response to the mouse or keyboard. Caja had crashed 5 times before Ubuntu did.

ProblemType: Bug
DistroRelease: Ubuntu 20.04
Package: linux-image-5.11.0-37-generic 5.11.0-37.41~20.04.2
ProcVersionSignature: Ubuntu 5.11.0-37.41~20.04.2-generic 5.11.22
Uname: Linux 5.11.0-37-generic x86_64
ApportVersion: 2.20.11-0ubuntu27.20
Architecture: amd64
CasperMD5CheckResult: skip
CurrentDesktop: MATE
Date: Thu Sep 30 16:30:21 2021
SourcePackage: linux-signed-hwe-5.11
UpgradeStatus: No upgrade log present (probably fresh install)