3GPP 38.300 v19.3.0 — the document's own text
16.9.5 Sidelink Discovery
The UE may perform NR sidelink discovery while in-coverage or out-of-coverage for non-relay operation.
The Relay discovery mechanism described in clause 16.12.3 (except the U2N Relay specific threshold based discovery message transmission and U2N Relay specific resource allocation mode restriction) is also applied to sidelink discovery.