No opinion on the patch itself. From afar, adding a new class + service looks like a new feature to me but I'm not much into the topic.

Thanks for the review@nicolas-grekas, I have applied all suggestions. Let's wait for@kbond's take on the patch then. I would hope this makes it to 6.4, but since the issue(not being able to use Messenger transports using Symfony Serializer with Scheduler) has existed already over a year, waiting a little bit more (for 7.3) doesn't make a huge difference for me.

Adding new classes or non private methods

From themaintenance doc. Strictly following this means this is a feature.

Ok, thanks, rebased on7.3 as a new feature.

Thank you@valtzu.