While Sales Forecast Accuracy is delivered through X-functional effort, what should be the RACI (Specifically "Accountable") for SFA?

Typically for SFA (and it can vary by organization):
R is the Sales Team, Data analysts that support the Sales
A is the Sales Director or Business leadership
C is Marketing, Planning, Finance, and other teams
I  is Management, functional leadership, and others

The forecast is and always should be owned by the sales and marketing teams. It is their accountability to deliver to that forecast in that end and they need to own it. The demand planning team in supply chain and the technology team are responsible to deliver what the models predict but the situational awareness of the market and interpretation is what sales should be responsible for in terms of fine tuning the forecast and every such modification can help train the ML models for the future model forecasting accuracy to continue improving and driving credibility within the S&M team.