Change a Drupal 9/10 system message to say what you want it to say
- modern Drupal 8 9 10 11 override message warning alert information text
- overriding message strings
- customize Drupal messages shown to users
The easiest way to do this is actually with string overrides.
grep your codebase for a part of the message you want to change, because you need to get the original source code to have an exact match on the string, including exactly how much it includes or doesn’t include, and any variable names it has that are substituted for something dynamic in the message.
https://drupal.stackexchange.com/a/261153/4195
Modules for this
Update: There are of course modules for this.
Background notes
https://stackoverflow.com/questions/38788080/remove-default-message-in-drupal-8
https://drupal.stackexchange.com/questions/212635/how-do-i-programmatically-change-a-system-message
Changes in Drupal 8.5: No more drupal_set_message https://www.drupal.org/node/2774931
Custom system messages
In addition to changing messages you may want to wholly create your own.
I like the Configuration Construction Kit approach (that is largely what Drutopia is) but actually would prefer that alerts not be a content type, it clutters the content interface. Maybe if only
https://www.drupal.org/project/alerts
Side note on Sitewide Alerts, someone wanted to and possibly did make it fieldable: 9 - How to make a custom entity fieldable? - Drupal Answers