I was interested in the technicalities around releasing something into the public domain and found that there is precedent and case law around it already in the US:

“[T]he author or proprietor of any work made the subject of copyright by the Copyright Law may abandon his literary property in the work before he has published it, or his copyright in it after he has done so; but he must abandon it by some overt act which manifests his purpose to surrender his rights in the work, and to allow the public to copy it.”[0]

[0] https://www.lawcatalog.com/media/productattach/l/j/ljp_694pu...