Singularity build failure due to groupadd for openssh-client installation

In Singularity when building under fake-root anything Ubuntu based with in %post either apt update -y or apt install -y openssh-client or their apt-get versions or with -f in the definition file fails fatally with groupadd: failure while writing changes to /etc/group addgroup: `/sbin/groupadd -g 101 ssh' returned error code 10. Exiting. Errors were encountered while processing: openssh-client E: Sub-process /usr/bin/dpkg returned an error code (1) FATAL: While performing build: while running engine: exit status 100 I see why adding a user is an issue, but yum update works fine in Rocky 9 (I cannot switch to it due to some requirements). This is on a cluster where I do NOT have root priviledges and have to use Singularity and docker isn't available —the base OS is CentOS 7 and glibc issues are insurmountable. I have tried a bunch of different Ubuntu images, ranging from Nvidia's Docker Ubuntu image and officially signed to unsigned Singularity images. Conda can install ssh, but the issue is apt update fails and I cannot work around it. I feel like I missing something obvious based on the lack of much on this online...