The eLTSS FHIR Implementation Guide will provide an official compilation of all the FHIR-related artifacts and documentation needed to enable exchange of eLTSS Dataset via FHIR.
Located at: https://hl7.org/fhir/us/eltss/
Build output https://build.fhir.org/ig/HL7/eLTSS/index.html
Build QA report https://build.fhir.org/ig/HL7/eLTSS/qa.html