How are you selecting feeds to download? If you use a cloud/self hosted RSS service you can get a feed of articles you star. From there you can use a desktop feed reader to download the starred feed to your kindle:
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Calibre can download news articles as .epub files, and supports transferring them to the kindle via USB. It can extract webpage text from non full-content feeds in a customizable way with Python.
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KOreader’s RSS feature stores feed items as .epub files as well, but it’s not as customizable. It does support full text extraction, but you don’t get any options to customize the output as far as I can tell.
EweSticker on fdroid is a keyboard that you can load gifs into, that’s the closest I’ve found.