NASA OIG Follow-up to May 2019 Audit of Europa Mission: Congressional Launch Vehicle Mandate, NASA OIG
"NASA's renewed focus on returning humans to the Moon on an accelerated timetable means that an SLS will not be available to launch the Clipper mission to Europa before 2025 at the earliest. Given all of the foregoing factors, we urge Congress to consider removing the requirement that NASA launch the Europa Clipper on an SLS and allow the Agency to decide whether to use an SLS or a commercial vehicle based on cost, schedule, vehicle availability, and impact on science requirements."
NASA OIG Audit: Management Of NASA's Europa Mission, NASA OIG, earlier post
"In addition, although Congress directed NASA to use the SLS to launch the Clipper, it is unlikely to be available by the congressionally mandated 2023 date and therefore the Agency continues to maintain spacecraft capabilities to accommodate both the SLS and two commercial launch vehicles, the Delta IV Heavy and Falcon Heavy."