You can try some fanfiction websites like Archive of Our Own (AO3). It has a large collection of Legend of Korra fanfictions. You just need to search for 'Legend of Korra' in the search bar, and then you can find a lot of stories to read. However, it's not for watching in the traditional sense as fanfictions are mainly text - based.
The Legend of Korra comics are definitely worth a read. They capture the essence of the franchise and bring fresh perspectives. The quality of the storytelling and the visuals make them a great addition to the series.
The 'lemon' aspect might be a bit hard to come by in a clean way as it often involves inappropriate content. But for normal Korra and Mako fanfictions, you could also try FanFiction.net. Some stories there might show their relationship developing, their adventures together, and how they support each other, which can be really interesting to read.
If you're a fan of the Avatar: The Legend of Korra series, it might be worth playing. It can offer more in - depth stories about the characters you love.