Background about Puerto Rico plans

Like most of you, I'm in the mainland U.S. and seldom work on plans (either dual-qualified or stand-alone) that cover employees from Puerto Rico.  However, I occasionally need to answer questions about those plans, especially regarding coverage and non-discrimination testing.

Are there any good resources available?  From 2018, I'm aware of this document:  https://documents.popular.com/pdfs/PFS/02_Puerto_Rico_Qualified_Plan_Discrimination_Testing_and_Reporting.pdf

We're proud of our search engine -- something to try is "Puerto Rico" as a search term --

https://benefitslink.com/search/index.cgi?textQuery=Puerto+Rico&sort=2&level=all_words&datasource=MYDB

Thanks, Dave.  Looking through the 2020 results, I didn't see anything regarding the coverage and non-discrimination testing rules for Puerto Rico plans.