There was some support for this in the form of client application addons (Firebase, etc), however, those meant the use of the delegation endpoint which is now unavailable for new accounts given it’s part of legacy flows.
At this time, there’s no counterpart to that on the new API surface that was introduced for OIDC compliance and your own API authorization. Having said that, this gap is something that is identified and there are discussions on introducing built-in functionality to better address those scenarios where the downstream API is not directly under your control and as such cannot also directly accept Auth0 issued tokens. However, due to this current gap, for now you’ll have to broker yourself that exchange between the different authorization forms - from the Auth0 issued access token to the format accepted by the downstream provider.