Issue starting after upgrading the Onpremise version : 9.1. we have the same issue with Online version.

Repro :

Queue> Queue Item I am working on > select one of type(type can be task,case, email and many more) > on top flow > select workflow (ondemand workflow created for that specific entity(type) is only appearing not queue Item workflow).

Impact : We have no other OOB option to run ondemand workflow on Queueitem entity.

Issue is same as described in the community : https://community.dynamics.com/blogs/post/?postid=8c16eead-3199-4c6b-b766-150ea66cdb28 , We have now the same behavior in UI as well, which is same for vanilla instance(onprem and online)

Checking this is a product behavior change but need a solution for the requirement.