I've told my team anyone is welcome to ask for a retro whenever for any reason, but we don't make them recurring meetings because there is too much of a temptation to find something wrong to fill the time.
By contrast, I've worked with scrum masters who were strict about the process and insisted _every_ retro needed to have at least one improvmenet or action item out of it, preferably more. I found this pointless and I've rarely seen them actually followed up on.
But people seem to love them.
I'd prefer to spend that time putting my head down and grinding through whatever sucky thing people were otherwise whining about.
If the EM is not there, those are not actionable. What we try to do is: do the retro by ourselves, and invite the EM at the end of there is stuff for them. Usually they are not available though...
The only thing on that list I've ever liked is the velocity charts. And the only reason I liked them is that it helped me give a slightly less made up date to my own bosses to explain when something might ship.
Over the years I've found that devs have been the one who like retros. Or at least a certain subset of them. When I've been an EM I would try to get rid of them, only to have them requested by my teams. Who knew.