Installed mailspring 1.9.2 on Debian Bullseye
First attempt to run binary failed with:
mailspring: error while loading shared libraries: libXss.so.1: cannot open shared object file: No such file or directory
apt install libxss1:amd64
fixes this.
I realize libxss1 is probably already installed on most system, but mine started is primarily i386 based
I’d never installed an amb64 package that depended on libxss1 before.