The set arrtibutes will be lost.

Good catch, thank you.

How about Url::mergeOptions():
https://git.drupalcode.org/project/drupal/-/blob/9.4.x/core/lib/Drupal/C...

Looks like less hustle and more compact in there?

Feel free to update it.

jaydev bhatt → made their first commit to this issue’s fork.

Updated the method from setOptions() to mergeOptions() as suggested by @gausarts to preserve existing attributes while adding the ultimenu__link class.
Moving to "Needs review" for further verification and testing.

Thank you all for contributions and extra finding.