I have looked through the issues and can't find one to match this - sincere apologies if I've missed it and this is a duplicate.

In section 4.1.1 there's a note that points to a 5 year old email from @dlongley raising the possibility of a DID resolver returning info about a service identified by type rather than by ID. @ChristopherA was not supportive!

However, we use exactly this kind of request in a GS1-Conformant resolver. That is, you can request a particular type of associated resource. We use link relation types for this and have a simple parameter of linkType so that https://id.gs1.org/01/09506000164908?linkType=gs1:certificationInfo redirects to a resource that, in this case, gives you a load of certificates related to the product identified by the GTIN 9506000164908. https://id.gs1.org/01/09506000164908?linkType=gs1:sustainabilityInfo redirects to the recycling info and so on. (the gs1 prefix refers to our namespace. The set of link types we define is managed under our standards process).

This is done by leveraging the Linkset, as defined by RFC9264 and you can get the whole linkset with curl -H "Accept: application/linkset+json" https://id.gs1.org/01/09506000164908.

What happens if you have multiple target resources of the same type? Step forward HTTP Response code 300 :-) We've implemented this in the open source version of the resolver but it's not in the production service yet so don't go trying it.

I'm not suggesting a wholesale adoption of this approach in DID Resolution, merely pointing out that requesting a resource by type is useful and has been thought about and engineered in a nearby context. If there is support within the WG for identifying service endpoints by type, the basic approach might be useful.

No one here will care but the use of RFC9264 and the linkType parameter to control resolver behavior is included in ISO/IEC 18975, currently at FDIS stage (Final Draft International Standard) which means that, unless something goes horribly wrong, it will be an ISO/IEC standard before the end of the year. Of more importance here is that it's cited multiple times in the UN Transparency Protocol work being led by Steve Capell. What that work calls an Identity Resolver, or, informally, a link resolver, has this kind of thing in mind.