We will have a PGP Key Signing at the ApacheConEU 2019. It will happen Thursday, 13:00-14:00 in the Hackathon room.
Remember: you can always sign keys individually throughout the conference. Feel free to ask around: if you meet other people from your project in person, they often will be willing to sign keys. Some people print up simple business cards or small slips of paper with their name, email, and PGP key fingerprints to pass out.