Remove Read More and display full text

Add this code to the Custom CSS field on the Appearance tab of your RSS Feed widget’s settings:

.global-styles,
[id^="eapps-rss-feed"]
[class^="Shortener__Outer"] {
  max-height: none;
}

.global-styles,
[id^="eapps-rss-feed"]
[class^="Text__Container"] >
[class^="Text__Control"] {
  display: none;
}