Rarely do any AI companies share their data sources. The way I think of it is...Don't ask for a specific artists' style or give it examples to copy. Don't give trademarked character names, and if you're worried about it, do a reverse image search using tineye or similar to verify it's not a close copy. If you're specific in your prompts, your response will be so specific that it's just yours. It's extremely unlikely someone will get the same thing if you're specific enough in the context of your conversation. For example, here's "A visual novel scene with a detective standing in the rain looking at a body on the ground in front of a hotel". That's quite specific, but you can get far more specific to be more...thematic. I would recommend that you work on putting your story in and make whatever program you're using familiar. Then try to get images that match your story with really long prompts that make it hard to be copies of something already out there.
Viewing post in Question about the AI resources
I'll be honest, that still makes me a little uncomfortable. Sure, if I'm precise enough the chances of directly copying someone are lower, but it was still trained on stolen art and may still have elements of that unwilling artist that I can't pick up on. I'd rather go into it knowing that it was trained on art that they got permission to use first.
The only results I can find for fully artist-approved training is the new Adobe Firefly stuff, but I'm not sure how good that is because it's still pretty new and just uses Adobe stock images.