Today marks the day when my game with #OKD is over because:

1) I am stupid
2) I run it on on old hardware

The most recent upgrade gave me this:

Txn Rebase on /org/projectatomic/rpmostree1/fedora_coreos failed: Sanity-checking final rootfs: bwrap(/usr/bin/true): Child process stopped by signal 0

You can try looking it up and confirm either #1, #2 or both.

@ly2en how do you get on idea #1? Based on https://access.redhat.com/solutions/7033342 ? I did not find much hints. Good luck.
OpenShift upgrade to 4.13 is getting stuck with 'Child process stopped by signal 0' - Red Hat Customer Portal

Nodes are degraded after failing to run rpm-ostree rebase command due to Child process stopped by signal 0 after initiating the upgrade to RHOCP 4.13 Degraded Machine: and Degraded Reason: failed to update OS to quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:888eda510e3c80bca8a43a939880543a0789e42cc1732c442c532d4575bb9692 : error running rpm-ostree rebase --experimental ostree-unverified-registry:quay.io/openshift-release-dev/ocp-v4.0-art-dev@sha256:888eda510e3c80bca8a43a939880543a0789e42cc1732c442c532d4575bb9692: ESC[0mESC[31merror: ESC[0mSanity-checking final rootfs: bwrap(/usr/bin/true): Child process stopped by signal 0

Red Hat Customer Portal
@DG7PC with 4.20 I have moved the cluster towards SCOS 10.0 and my x86-64-v2 architecture level is too low for 10+. The true error was in the journal logs while this was thrown up right into my face on STDERR.