eReassign updated today, from no listings at all, to only clerks and mail handlers, but no open letter carrier positions anywhere. Why is this?

They stopped posting July of last year. You just have to submit a request and wait.

Previously, employees wishing to transfer could request transfer in eReassign up to the last day of the 21-day posting period. Since that posting period is no longer necessary, and to further facilitate the timely filling of full-time regular opportunities, employees wishing to transfer into an installation must have an active transfer request in
eReassign the date the opportunity first becomes available.

Thanks. This process could be easier...

Yes it's frustrating not being able to know if there's any vacancies and if you'll be waiting for a month or a year or more. And with the cca conversion ratios it's made transferring a lot harder.