Springer Nature Experiments has a standalone Stanza now for EZProxy. Please find the most up to date version of this stanza on the OCLC Stanza page here: https://help.oclc.org/Library_Management/EZproxy/Database_stanzas
For Reference the Stanza below was updated on 31 May 2019:
Title Springer Nature Experiments (updated 20190531) URL https://experiments.springernature.com HJ http://experiments.springernature.com HJ springernature.com DJ springernature.com
For hosted proxy service customers in the US using self-service this is the record to place in your Include File:
IncludeFile databases/springerprotocols.txt