We saw that Github has no swap activated. So we activated it using thejerrybao/setup-swap-space@v1 step with 64GB which should be plenty enough.
It happens sporadically, but when it happens it happens always at the same place, during this second apt update.
Here is something else interesting:
2025-07-31T09:58:48.5188156Z [0m[1;30m[π³|[0mπ¨[0m] [0m total used free shared buff/cache available
2025-07-31T09:58:48.5189232Z [0m[1;30m[π³|[0mπ¨[0m] [0mMem: 31Gi 3.8Gi 15Gi 2.3Gi 14Gi 27Gi
2025-07-31T09:58:48.5190178Z [0m[1;30m[π³|[0mπ¨[0m] [0mSwap: 63Gi 0B 63Gi
2025-07-31T09:58:48.5643835Z [0m[1;30m[π³|[0mπ¨[0m] [0mFilesystem Size Used Avail Use% Mounted on
2025-07-31T09:58:48.5645400Z [0m[1;30m[π³|[0mπ¨[0m] [0mtmpfs 32G 2.3G 29G 8% /
2025-07-31T09:58:48.5646148Z [0m[1;30m[π³|[0mπ¨[0m] [0mtmpfs 32G 12M 32G 1% /tmp
2025-07-31T09:58:48.5646870Z [0m[1;30m[π³|[0mπ¨[0m] [0mtmpfs 32G 0 32G 0% /var/tmp
2025-07-31T09:58:48.5647587Z [0m[1;30m[π³|[0mπ¨[0m] [0mtmpfs 32G 0 32G 0% /run/user/0
2025-07-31T09:58:48.5648279Z [0m[1;30m[π³|[0mπ¨[0m] [0mtmpfs 64M 0 64M 0% /dev
2025-07-31T09:58:48.5648972Z [0m[1;30m[π³|[0mπ¨[0m] [0m/dev/root 290G 105G 186G 37% /tmp/overlay
2025-07-31T09:58:48.5669589Z [0m[1;30m[π³|[0mπ¨[0m] [0m------------------------------------------------------------------
2025-07-31T09:58:48.5670721Z [0m[1;30m[π³|[0mπ¨[0m] [0m------------------------------------------------------------------------------------
2025-07-31T09:58:48.5671415Z [0m[1;30m[π³|[0mπ¨[0m] [0mInstalling NodeRED
2025-07-31T09:58:49.1670560Z [0m[1;30m[π³|[0mπ¨[0m] [0mHit:1 http://deb.debian.org/debian bookworm InRelease
2025-07-31T09:58:49.1677442Z [0m[1;30m[π³|[0mπ¨[0m] [0mHit:2 http://github.armbian.com/configng stable InRelease
2025-07-31T09:58:49.1680378Z [0m[1;30m[π³|[0mπ¨[0m] [0mHit:3 http://deb.debian.org/debian bookworm-updates InRelease
2025-07-31T09:58:49.1682868Z [0m[1;30m[π³|[0mπ¨[0m] [0mHit:4 http://deb.debian.org/debian bookworm-backports InRelease
2025-07-31T09:58:49.1685589Z [0m[1;30m[π³|[0mπ¨[0m] [0mHit:5 http://security.debian.org bookworm-security InRelease
2025-07-31T09:58:58.1575506Z [0m[1;30m[π³|[0mπ¨[0m] [0mReading package lists...
2025-07-31T09:58:58.2559413Z [0m[1;30m[π³|[0mπ¨[0m] [0mE: Could not read from /var/lib/apt/lists/deb.debian.org_debian_dists_bookworm-backports_InRelease - getline (12: Cannot allocate memory)
2025-07-31T09:58:58.2561244Z [0m[1;30m[π³|[0mπ¨[0m] [0mE: The repository 'http://deb.debian.org/debian bookworm-backports InRelease' provides only weak security information.
We added a free -h and a df -h command. It seems that the memleak is in apt-get update because there is around 78GBi of RAM available.
No we did not build on bare metal for a long time.