@starfrost Rather than generally biased (which I agree can be a bit of a misnomer as most content can be deemed biased in some way) I would be looking at specific aspects such as racist, medically harmful, misogynist, ableist, abusive etceteras.
Many general tools struggle because they are general, and without a clearly defined purpose and use-case. That makes it hard to gauge success but also hard to gauge appropriateness for anything.
When services/products have more clearly defined goals and purposes there are models for impact assessment that can be made use of as part of a development process.
I outline a couple of them at the end of this post: https://axbom.com/digital-compassion-human-act/