MasterSoft24/xUbuntu_16.10 not signed?

[typoworx-de]

Looks similar to issue mentioned in #74

This didn't help

wget http://download.opensuse.org/repositories/home:/MasterSoft24/xUbuntu_16.10/Release.key -O - | sudo apt-key add -
OK

sudo apt-get update still is broken saying GPG-ERROR and KEYEXPIRED 1623474241.

I'm unable to install :-(