Cannot use APT repo snapshots

Hi folks–
Has anyone successfully used an APT proxy snapshot?
Configuration is OSS 3.38.0-01

My use case is to install Ubuntu from a proxy snapshot.
I am able to install from a proxy that tracks the public Ubuntu repository. But snapshots of that proxy have incomplete metadata and are missing items expected by the installer.
Does anyone know how to get a complete snapshot of the metadata?

Failures from the installer include:

Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Get:4 http://repo-proxy.sn.stratus.com/repository/Barracuda-impish/snapshots/apr02 impish InRelease [270 kB]
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Ign:5 http://repo-proxy.sn.stratus.com/repository/Barracuda-impish/snapshots/apr02 impish-updates InRelease
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Ign:6 http://repo-proxy.sn.stratus.com/repository/Barracuda-impish/snapshots/apr02 impish-backports InRelease
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Ign:7 http://repo-proxy.sn.stratus.com/repository/Barracuda-impish/snapshots/apr02 impish-security InRelease
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Get:2 file:/cdrom impish Release [1599 B]
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Get:8 file:/cdrom impish Release.gpg [659 B]
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Get:8 file:/cdrom impish Release.gpg [659 B]
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Err:9 http://repo-proxy.sn.stratus.com/repository/Barracuda-impish/snapshots/apr02 impish-updates Release
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: 404 Not Found [IP: 3d00:feed:face:24:204:fcff:fe00:420a 80]
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Err:10 http://repo-proxy.sn.stratus.com/repository/Barracuda-impish/snapshots/apr02 impish-backports Release
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: 404 Not Found [IP: 3d00:feed:face:24:204:fcff:fe00:420a 80]
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: Err:11 http://repo-proxy.sn.stratus.com/repository/Barracuda-impish/snapshots/apr02 impish-security Release
Apr 2 13:10:41 ubuntu-server subiquity_log.1698[1877]: 404 Not Found [IP: 3d00:feed:face:24:204:fcff:fe00:420a 80]