Thanks. And for starred items? Is there a way?

Hmm... you can add the feature if you modify the file
controllers/Rss.php

Search for this code (Line 36/37)

if(\F3::get('PARAMS["tag"]')!=null)
$options['tag'] = \F3::get('PARAMS["tag"]');

and add the following lines direct behind them:

if(\F3::get('PARAMS["type"]')!=null)
$options['type'] = \F3::get('PARAMS["type"]');

Then you can modify your feed with ".../feed?tag=<tagname>&type=<type>"
As type you can use "unread" or "starred"

I already forked this change in GitHub, so it is maybe in the next version of selfoss...