I’ve Put Up A Free Collection of RSS Tools at RSSGizmos.com
RSSGizmos.com currently offers the following tools in an ad-free, cookie-free, yes-it-is-free environment:
Kebberfegg — Make keyword-based RSS feeds for a dozen different sources including Reddit, Bing, and Google News.
WikiRSS — Search Wikipedia for articles which contain RSS feeds as part of their Wikidata.
CountryFeed — Make country-specific RSS feeds using Bing News’ loc: syntax and get them bundled in an OPML file.
WordPress Preview — Preview and compare RSS feeds for WordPress.com tag and keyword searches.
Bing News Query Checker — Test and three different queries for a Bing News RSS feed.
RSS Feed Viewer — Preview an RSS feed.
Feed Freshness Checker — Analyze up to 20 feeds at a time for post age and frequency.
OPML Maker — Turn a bunch of RSS feeds into an OPML file.
OPML Peeler — Extract the RSS feeds from an OPML file to display them and make them available as a CSV file.
This site is static HTML instead of WordPress, so everything should work on your phone. I tested the site with an iPhone 6S and it was fine.