Some plugins for tt-rss.
Install to plugins.local folder of your tt-rss instance.
Unofficial documentation for hooks in TT-RSS
tt-rss-samples by fox himself.
Not so comprehensive Making Plugins introduction. Mainly telling that there is none.
A list of plugins provided by various sources.
Use the Feed Debug feature of tt-rss. (right click on feed->debug)
Check the event log.
Trigger updates manually by
sudo -u www-data php update.php --force-rehash --debug-feed feed_number_from_feed_debug
Bindmount init.php from tt-rss installation to your home directory for direct access.
sudo mount --bind source_file target_file
sudo chown user target_file