You are correct, Canvas doesn't have support for this yet, but we do plan to support it in the future.
The IMS LTI working group has a proposed specification in progress to add support for this as an additional capability similar to Names and Roles Provisioning Service to compliment LTI 1.3 and its use of OIDC. We have a few challenges we need to figure out as we work through adding this support. The specification allows for tools to not only register through the well known endpoint, but to also send through updates. We'd like to support both capabilities.
With more schools/institutions concerned about what data they are approving access to, we'll have to consider how updates can go through an approval process by Canvas admins before they can work within their respective Canvas accounts.