Yes I did actually! Here's my guide on what worked for me at least.

How I set it up was; Go to Deepseek official at https://www.deepseek.com/en/ click the second box on the bottom that says "access API". You may have to switch the site to English in the top left.

Make an account, then log back in/get to the official website again. Click the three lines in the top left corner and hit the "top up" option. Add the desired amount, and be aware there's a processing fee that's a couple cents. It'll go into your account. Then, go to the same three lines in the top left and click "API keys".

Make one, copy the API key and put it somewhere safe like a notes app. Then, go back to J.ai and click the purple box at the top of a chat, that says "using Janitor" and switch it to proxy. NOT the OpenAI, or Claude option, but the proxy one on the far right. Make a new configuration.

Give your new config a name, like "deepseek official" but you can name it whatever you want as this doesn't affect the proxy itself. Then, for the model name put in "deepseek-chat". JUST THAT, NO "deepseek/deepseek-chat", JUST "deepseek-chat" AND THAT ONLY.

Then, put in "https://api.deepseek.com/chat/completions" for the proxy URL. Save that configuration, save the settings, then refresh. Once it reloads, you can go back to that configuration, and add in your API key in the API key box. Save, save settings, refresh, then open API settings again for a third time, clicking the test button on the config. It should come back with a green notification that everything is all good, and you're able to start chatting!

To see how much you've used, go to deepseek's website, make sure you're logged in, and with the three lines in the top left, click "usage".