Sometimes an upgrade failure can retrieve useful information like the info highlighted in bz 1998796, but often a pulp3 migration can fail with much simpler information.

For example, seen in a migration failure:
───────────────────────────────────────────────────────────────────────
var/log/foreman-maintain/foreman-maintain.log:
...
rake aborted!^M
ForemanTasks::TaskError: Task 28fd76c4-d68c-4e50-a188-db:3c:3f:f6:83:86 Katello::Errors::Pulp3Error: 1 subtask(s) failed for task group /pulp/api/v3/task-groups/51172b91-afcd-4865-b093-73:f6:e8:37:2b:16/.^M
/opt/theforeman/tfm/obfuscateduser1/usr/share/gems/gems/katello-128.0.0.95/lib/katello/tasks/pulp3_migration.rake:42:in `block (2 levels) in <top (required)>'^M
/opt/rh/rh-ruby25/obfuscateduser1/usr/share/gems/gems/rake-12.3.3/exe/rake:27:in `<top (required)>'^M
Tasks: TOP => katello:pulp3_migration^M
(See full trace by running task with --trace)^M

E, 2021-11-30 20:39:42-0500 #10271 ERROR – : Failed executing foreman-rake katello:pulp3_migration, exit status 1 (ForemanMaintain::Error::ExecutionError)
/usr/share/gems/gems/foreman_maintain-0.7.13/lib/foreman_maintain/utils/command_runner.rb:54:in `execution_error'
/usr/share/gems/gems/foreman_maintain-0.7.13/lib/foreman_maintain/concerns/system_helpers.rb:68:in `execute!'
/usr/share/gems/gems/foreman_maintain-0.7.13/definitions/procedures/content/prepare.rb:10:in `run'
/usr/share/gems/gems/foreman_maintain-0.7.13/lib/foreman_maintain/executable.rb:139:in `_run_'
...
───────────────────────────────────────────────────────────────────────
From the dynflow task info:
Error:

Katello::Errors::Pulp3Error

1 subtask(s) failed for task group /pulp/api/v3/task-groups/51172b91-afcd-4865-b093-c5f574b6f388/.
───────────────────────────────────────────────────────────────────────

We can find this task info in Dynflow but that information is also limited, seen here:
───────────────────────────────────────────────────────────────────────
task_groups:

• pulp_href: "/pulp/api/v3/task-groups/51172b91-afcd-4865-b093-c5f574b6f388/"
  description: Migration Sub-tasks
  all_tasks_dispatched: true
  waiting: 0
  skipped: 0
  running: 0
  completed: 103
  canceled: 0
  failed: 1
  group_progress_reports:
• message: Distribution creation
  code: create.distribution
  total: 183
  done: 182
• message: Repo version creation
  code: create.repo_version
  total: 103
  done: 103
  poll_attempts:
  total: 1162
  failed: 1
  ───────────────────────────────────────────────────────────────────────

So this helps the user identify that a distributor had trouble migrating, but isn't helpful with other information, like which distributor caused an issue when migrating, and also why that issue occurred is left out.