git delete remotes: remote refs do not exist

Question

In short;

• How can I delete remote multiple merged remotes?

More background;

I have a git repo with tens of remotes which have been merge

Answer 1

Are those branches removed from the remote (origin)? If yes, you can simply do

git fetch --prune origin

Otherwise they might return even after you delete them locally.

Update: Looking at your command again, it looks like you're building it incorrectly. You probably want

git push origin --delete myBranch-1234

but instead you are doing something like

git push origin --delete origin/myBranch-1234