3GPP 24.501 v20.0.0 — the document's own text
8.2.10.10 Non-3GPP access path switching indication
Taught in 4. Inside TS 24.501, the document at the centre (CT1 — the group that writes what your phone says, overview).
The UE may include this IE when the Payload container type IE is set to "N1 SM information" to indicate whether the UE supports the non-3GPP access path switching for the PDU session.