The coreboot community is present at a number of conferences over the year, usually at FOSDEM, OSFC, and the Chaos Communication Congress.
The kind of presence differs, but there's usually a booth or other kind of gathering where everybody is welcome to say hello and to learn more about coreboot.
Depending on the nature of the conference, coreboot developers might bring their development kit with them and conduct development sessions.
Open Source Firmware at Facebook by David Hendricks and Andrea Barberio at FOSDEM 2019 (video) (slides) (2019-02-03)
Open Source Firmware - A love story by Philipp Deppenwiese at 35c3 (slides) (2018-12-27)