when dumpcap is stopped it prints a short packets stats report. Example
Packets received/dropped on interface 'eno2': 138657725/12413592 (pcap:12413591/dumpcap:1/flushed:0/ps_ifdrop:109) (91.8%)
Source code: https://github.com/wireshark/wireshark/blob/master/dumpcap.c#L5456
It it possible to get this report periodically (without stopping dumpcap)
thanks