quite low priority, but I wanted to write it down just in case I stumble across it again in the future.
(and maybe the same is true for other error messages and it confuses user)
When developing Matomo doesn't have write permission to
plugins/. This doesn't matter as it isn't needed for things apart from the marketplace.
When one tries to download something from the marketplace this error message appears rightfully:
The issue is that there is no way to get rid of the notification. Pressing the x only closes it with JS, but as it is rendered by Twig it will reappear on every page even when it doesn't matter anymore.
removes it from the session and gets finally rid of the message (ending the session in another way would also work).