Can't get drush 9 aliases back to work after composer install

[rotemreiss]

We have added some drush aliases for a multi-site project, the aliases were converted from the previous syntax to the Drush 9 syntax (.yml files).

I went over the documentation, and also saw the previous issues, notes and changes on this GitHub issue.

For some reason the aliases didn't work inside $ROOT/../drush/sites as documented, but did work inside $ROOT/drush/sites, and I also had to use the format of [site].alias.yml and not [site].site.yml as on the documentation.

Another thing is that @greg-1-anderson wrote on his comment that

Only ~/.drush/sites et. al. are searched now.

So now I am really lost between the documentation, the comments, and the aliases that worked last week and were broken now after composer install.

Can someone please tell me what am I missing here?

** I've also tried to place the aliases in ~/.drush/sites/ (which didn't work).

[weitzman]

What version of drush are you using? Please paste output of `composer show drush/drush`

[greg-1-anderson]

Duplicate of aliases stop working after composer install on Drupal Stack Exchange. Saw this there first.