Trying multiple private keys against a pcap
META: this is really tool use not crypto and probably should be on superuser.

Open the PCAP file in Wireshark. Find the/a desired handshake; expand the handshake message containing the (server) Certificate message, the Certificates element, the first (EE) Certificate and the signedCertificate; click subjectPublicKeyInfo and rightclick,ExportSelected to a file, for example pubkeyfile.

Write a shell script (or CMD or PS or whatever) to run openssl pkey -in privkeyfile -pubout -outform der and compare the result to pubkeyfile; in Bourne-type shell this could be:

 for p in privkey*; do 
     if openssl pkey -in $p -pubout -outform der | cmp -s - pubkeyfile
     then echo FOUND $p; fi; done