There are two of the four levels of evaluation that should be conducted during every delivery of the course. Level 1 (reaction surveys) and level 2 (tests). Reaction surveys include feedback from the attendees on whether they liked the course itself, as well as the trainer.
Level 2 is meant to assess whether the attendees are actually learning anything. It takes place during the training through all the practice/application opportunities built into the design of the course. Getting feedback from stakeholders is not a common way to evaluate training, unless that feedback comes with documentation in the form of records or reports retrieved post-training. That is the deepest level of evaluation (level 4).
Level 3 involves observing the trainees on the job (post training) to see if they actually applied what they learned. This is where managers/supervisors come into play. They’re in the best position to conduct the observation with a performance checklist.