Comment 13 for bug 2003669

Many thanks for re-testing, Ingo!

Adding the PPA works for me:
$ sudo add-apt-repository ppa:fheimes/lp2022088
Repository: 'deb https://ppa.launchpadcontent.net/fheimes/lp2022088/ubuntu/ lunar main'
Description:
lp2022088
More info: https://launchpad.net/~fheimes/+archive/ubuntu/lp2022088
Adding repository.
Press [ENTER] to continue or Ctrl-c to cancel.
Adding deb entry to /etc/apt/sources.list.d/fheimes-ubuntu-lp2022088-lunar.list
Adding disabled deb-src entry to /etc/apt/sources.list.d/fheimes-ubuntu-lp2022088-lunar.list
Adding key to /etc/apt/trusted.gpg.d/fheimes-ubuntu-lp2022088.gpg with fingerprint 73E9E91F16C43C45C621AE3EDF0A28DEFAFEB468
Hit:1 http://ports.ubuntu.com/ubuntu-ports lunar InRelease
Get:2 http://ports.ubuntu.com/ubuntu-ports lunar-updates InRelease [109 kB]
Hit:3 https://ppa.launchpadcontent.net/arighi/s390x-test/ubuntu lunar InRelease
Get:4 http://ports.ubuntu.com/ubuntu-ports lunar-backports InRelease [99.8 kB]
Get:5 http://ports.ubuntu.com/ubuntu-ports lunar-security InRelease [109 kB]
Hit:6 https://ppa.launchpadcontent.net/canonical-kernel-team/bootstrap/ubuntu lunar InRelease
Get:7 http://ports.ubuntu.com/ubuntu-ports lunar-updates/main s390x Packages [118 kB]
Get:8 http://ports.ubuntu.com/ubuntu-ports lunar-updates/universe s390x Packages [57.8 kB]
Get:9 https://ppa.launchpadcontent.net/fheimes/lp2022088/ubuntu lunar InRelease [18.0 kB]
Get:10 https://ppa.launchpadcontent.net/fheimes/lp2022088/ubuntu lunar/main s390x Packages [912 B]
Get:11 https://ppa.launchpadcontent.net/fheimes/lp2022088/ubuntu lunar/main Translation-en [468 B]
Fetched 512 kB in 2s (278 kB/s)
Reading package lists... Done

Proxy / firewall?