Man pages matching name pcap_set_immediate_mode in section 3pcap:

pcap_set_immediate_mode.3pcap.en	debian 10 / libpcap0.8-dev
pcap_set_immediate_mode.3pcap.en	debian 11 / libpcap0.8-dev
pcap_set_immediate_mode.3pcap.en	debian 12 / libpcap0.8-dev