Useful Drupal modules

Click on the module name for notes, comments, patches.
Recommendations (for and against) are my personal opinion only and may be out of date. Feel free to email with corrections/suggestions.

Why haven't you mentioned Drupal 9? I will be adding this, but as of August 2021, this site you are reading is the only Drupal site of mine I've been able to upgrade to D9, so although you can check D9 compatibility status of all modules (use upgrade_status, it's superb) I can't speak from personal experience about any of them.

(1 modules in list)
Module name or machine name
Any text in the notes
Name D8 Personally Tested Last Updated
Comment Notify (comment_notify) 2018-12-15

d.o. page

"Essential"

Allows users to receive emails for replies to their comments (or optionally for all comments on a node).  Can be toggled by content type (although not by comment type, if you have more than one comment entity).  In permissions, you can also control which roles can subscribe.  Can also set it so the author of a node also automatically gets emailed for every comment.

I'm using three patches:

I also have a site which uses two comment types; I wrote a patch to turn off the notification checkbox for one of them.