Is there a roadmap or sort of checklist timeline on items that need to be completed and what projected date(s) interfaces would be released as officially supported?
https://docs.daml.com/daml/reference/interfaces.html
Thanks!
Interfaces are going to be released as part of Daml 2.4 in Early Access. This means essentially than the feature is opt-in and you cannot rely on it for production code, mostly because any language-related feature has the possibility of making breaking changes to the exact serialization of transactions. By the time the release is out, the bulk of the functionality needed to support it will be available throughout the stack to support it, with a few notable known exceptions that will be worked on as the feature moves towards General Availability, specifically support for interface subscriptions (reading transactions by interface ID) in Daml Script and Daml Triggers, as well as the implementation of persistence for interface payloads on the HTTP JSON API service (meaning that interface subscriptions will be available on the HTTP JSON API service but the data will be served from memory and not cached on the query store).
One place to check would be GitHub tags (1, 2); don’t read too much into the names of those tags. Note that they are not comprehensive, and largely reflect ledger API client changes at time of writing; as many of your questions have reflected client APIs e.g. Java API these may be of most interest to you.