I tested this on Bionic (albeit using Ubuntu Error Tracker retracing systems) and updating the ubuntu-dbgsym-kerying from -proposed allowed them to retrace crashes again so setting to verification-done.

2021-03-26 17:15:33,167:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Processing.
2021-03-26 17:15:33,219:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Decompressing to /tmp/tmprCylMh-swift.6d1
acc70-8e56-11eb-8af4-fa163e9b80e2.oopsid.core
2021-03-26 17:15:33,314:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Retracing 6d1acc70-8e56-11eb-8af4-fa163e9
b80e2:swift with sandbox-dir /srv/daisy.staging.ubuntu.com/devel/cache/Ubuntu 21.04/cache-uUsGBd/sandbox with cache /srv/daisy.staging.ubunt
u.com/devel/cache/Ubuntu 21.04/cache-uUsGBd/cache
2021-03-26 17:15:36,471:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Apport's return code was 1.
2021-03-26 17:15:36,471:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:ERROR: W:Download is performed unsandboxe
d as root as file '/srv/daisy.staging.ubuntu.com/devel/cache/Ubuntu 21.04/cache-uUsGBd/cache/Ubuntu 21.04/apt/var/lib/apt/lists/partial/arch
ive.ubuntu.com_ubuntu_dists_hirsute_InRelease' couldn't be accessed by user '_apt'. - pkgAcquire::Run (13: Permission denied), W:GPG error: 
http://ddebs.ubuntu.com hirsute Release: The following signatures were invalid: EXPKEYSIG C8CAB6595FDFF622 Ubuntu Debug Symbol Archive Autom
atic Signing Key (2016) <email address hidden>, E:The repository 'http://ddebs.ubuntu.com hirsute Release' is not signed., W:Upda
ting from such a repository can't be done securely, and is therefore disabled by default., W:See apt-secure(8) manpage for repository creati
on and user configuration details., W:GPG error: http://ddebs.ubuntu.com hirsute-updates Release: The following signatures were invalid: EXP
KEYSIG C8CAB6595FDFF622 Ubuntu Debug Symbol Archive Automatic Signing Key (2016) <email address hidden>, E:The repository 'http:/
/ddebs.ubuntu.com hirsute-updates Release' is not signed.
2021-03-26 17:15:36,471:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Will retry (6d1acc70-8e56-11eb-8af4-fa163
e9b80e2) due to a transient error.
2021-03-26 17:15:36,473:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Processing.
2021-03-26 17:15:36,657:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Decompressing to /tmp/tmpaSBRUl-swift.6d1
acc70-8e56-11eb-8af4-fa163e9b80e2.oopsid.core
2021-03-26 17:15:36,751:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Retracing 6d1acc70-8e56-11eb-8af4-fa163e9
b80e2:swift with sandbox-dir /srv/daisy.staging.ubuntu.com/devel/cache/Ubuntu 21.04/cache-uUsGBd/sandbox with cache /srv/daisy.staging.ubunt
u.com/devel/cache/Ubuntu 21.04/cache-uUsGBd/cache
2021-03-26 17:16:35,063:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Writing back to Cassandra
2021-03-26 17:16:35,150:19962:140010884187968:INFO:root:6d1acc70-8e56-11eb-8af4-fa163e9b80e2:swift:Successfully retraced.

ubuntu@juju-1124ad-devel-error-tracker-9:/srv/daisy.staging.ubuntu.com/devel-logs$ apt-cache policy ubuntu-dbgsym-keyring
ubuntu-dbgsym-keyring:
  Installed: 2018.09.18.1~18.04.1
  Candidate: 2018.09.18.1~18.04.1
  Version table:
 *** 2018.09.18.1~18.04.1 500
        500 http://archive.ubuntu.com/ubuntu bionic-proposed/universe amd64 Packages
        100 /var/lib/dpkg/status
     2018.09.18.1~18.04.0 500
        500 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu bionic-updates/universe amd64 Packages
     2018.02.28 500
        500 http://prodstack-zone-2.clouds.archive.ubuntu.com/ubuntu bionic/universe amd64 Packages