How in-game radar flags work in Source 2:

Every CCSPlayerController contains a m_bSpotted boolean and m_bSpottedByMask bitmask representing which players have direct line of sight to this pawn.

To force all enemies to appear on the official mini-map radar:

for (int i = 1; i <= 64; i++) {
    auto pController = GetPlayerControllerByIndex(i);
    if (!pController || !pController->m_bPawnIsAlive()) continue;
    auto pPawn = pController->m_hPlayerPawn().Get();
    if (pPawn && pPawn->m_iTeamNum() != pLocal->m_iTeamNum()) {
        pPawn->m_bSpotted() = true; // In-engine radar reveal
    }
}

Setting m_bSpotted = true also makes the native red radar dots appear for teammates without drawing external ESP. Very stealthy.

Simple 1-line memory modification that works cleanly.