GPT Trainer makes creating a custom ChatGPT instance extremely simple--and yet very flexible. You can train on files, URLs (with auto site crawling), and tables. There is also a Q & A feature I have not tried.

It was trivial to embed the bot on a web page, too. Five tacos from me--and remember that I don't write a lot of reviews good or bad because I'm not motivated to. This one motivated me.