I will chip in as a happy user of PlantText[1]. It allows you to edit PlantUML diagrams, renders them, and you can either download them as PNGs, SVG, or ASCII. I'm pretty sure you can also directly link to an image, although I'm not sure about ToS, so don't do it without fact-checking. Oh, and it saves your content locally.

[1]: https://www.planttext.com/.