I actually spent a lot of time when custom GPT's were first released researching the best way to train them. I created a custom GPT for LSL that is trained off not just public available data such as the wiki itself but updates from the blog, deprecated methods, custom user functions and other sources I myself have collected over the years. I'm not saying it's perfect and even with all the data it might still venture out online and bring back false information. But the amount of testing I've done and with the help of other SL people who have tested this with me it has done 100x better than vanilla gpt 4. Of course feedback is encouraged since all feedback would be used to train it.
https://chat.openai.com/g/g-8P0lGqMIy-lsl-guru