All WordPress blog support RSS, even though some aren't explicitly displaying an RSS button.
For the blogs that have RSS buttons, just click on the buttons and your browser should open a popup where you can select the RSS app you want to open the link, select.
If there isn't any RSS buttons or link, you can also modify the URL to get an RSS feed. Just add, at the end of a WordPress category to get a feed for the category or from the blog homepage to get a feed for all posts.
You will now see the opened feed window, where you can choose Akregator.