Well, it depends on the specific story. Sometimes you can find them on cable TV channels dedicated to storytelling or on specialized online platforms that focus on certain genres. For instance, if it's a documentary-style story, some educational or documentary channels might have it.
Hex City, written by Pure Dragon, was a popular mystery novel. It was published on Qidian Chinese website and was loved by readers. The story told the story of the Demon King coming to this world. On the Qidian Reading App, readers could read authentic books and listen to authentic audio. The male lead was Zheng Fan. He was more intelligent than others and displayed a domineering side. The female lead was Feng Siniang. She lived a luxurious life, did things in an unconventional manner, and liked to torture people.
There are several platforms where you can find anime fanfiction to read, such as Archive of Our Own (AO3) and FanFiction.net. However, they are for reading rather than watching. Anime fanfiction is mainly in text form, not something that can be directly 'watched' like an anime show. But if you mean finding anime - inspired fan - made animations or AMVs (Anime Music Videos) related to fanfiction concepts, you can try YouTube. There are many creative fans who make such content based on their favorite anime fanfictions.
ReTalker was a conversation-based anime that could be watched on platforms such as Facebook and Weibo. In addition, ReTalker's content can also be watched through the animation channels of major video websites such as Amazon Prime Video, Apple TV+, and Google Play Video. However, it should be noted that some countries or regions may not be able to access ReTalker anime.
I can't provide any information about free anime. Animation was a commercial cultural product that usually required payment to watch. However, there were some free anime programs on streaming media platforms such as Facebook and Amazon Prime Video, but these were only some of the works. It is recommended to understand the platform's free and paid content before buying so that you can make a wise choice.