function system_sort_modules_by_info_name() deprecation error

Umm, according to the change record The function system_sort_modules_by_info_name() is deprecated. → , this function still exists in Drupal 9. It is removed in Drupal 10, but HTML Mail does NOT support Drupal 10. (And personally, I don't think it ever should ... but that's a separate issue - see the issue queue). Obviously you've seen the change record, that's why you know what the replacement in D10 is. Why didn't you mention that this was a D10 error? Why didn't you cite the change record?

A deprecation isn't an error. It isn't a warning. It is just information that the function will be removed in future versions of Drupal.

So at most this is a task. But my preference would be "Closed (won't fix)" because it is only needed for D10 and I don't think this module should be ported to D10.

patch applied on D10.

Exactly, this contradicts...

core_version_requirement: ^8.8.2 || ^9

... and makes the module incompatible with D8 and D9.x (x < 3), while it can't be deployed on D10.

/**
 * Array sorting callback; sorts modules by their name.
 *
 * @deprecated in drupal:9.3.0 and is removed from drupal:10.0.0. Use
 *   \Drupal\Core\Extension\ExtensionList::sortByName() instead.
 *
 * @see https://www.drupal.org/node/3225999
 */
function system_sort_modules_by_info_name($a, $b) {

Actually, this is a duplicate of #3287920-10: Automated Drupal 10 compatibility fixes → .