With Super RSS Reader PRO, you can merge and display multiple RSS feeds as one. You can enter multiple RSS feed URLs in the URL field and select the "Merge RSS feeds into one" option.
Demo video
Shortcode option
If you are displaying RSS feed using Shortcode, then you can provide multiple RSS feed URLs to the urls parameter and set the parameter merge_feeds to 1. You can show the RSS feed source name using the show_source option.
You can find all the supported option for shortcode documentation page.
[srr_feed urls="https://feeds.feedburner.com/Makeuseof, https://www.nasa.gov/rss/dyn/breaking_news.rss" merge_feeds="1" show_source="above_title"]