Hello @mspr1nt
AMP plugin only modifies content which displays on the site (the serving html), and not the one served from various services like wp-json or RSS
As RSS content is non-AMP content it will served normally ( as normal WordPress site content) so “it” should not look for <amp-img>
tag instead “it” should look for <img>
tag, assuming this is your site and this is your feed URL, I am able to get images as below
eg image:
<figure class="wp-block-image size-large"><img loading="lazy" width="1920" height="1329" src="https://extratime.media/wp-content/uploads/2021/01/arsenal-vs-crystal-palace-EPL-predictionEPL-prediction.png" alt="Arsenal Vs Crystal Palace Epl Predictionepl Prediction" class="wp-image-31465" srcset="https://extratime.media/wp-content/uploads/2021/01/arsenal-vs-crystal-palace-EPL-predictionEPL-prediction.png 1920w, https://extratime.media/wp-content/uploads/2021/01/arsenal-vs-crystal-palace-EPL-predictionEPL-prediction-1536x1063.png 1536w, https://extratime.media/wp-content/uploads/2021/01/arsenal-vs-crystal-palace-EPL-predictionEPL-prediction-1200x831.png 1200w" sizes="(max-width: 1920px) 100vw, 1920px" /></figure>
Also, your RSS feed seems to be valid you can verify it here ( if it times out paste output of feed URL in input )
Also, do check this for RSS standards.
I will recommend asking further questions regarding RSS in WordPress Miscellaneous Support Forum.