I got confused between Twitter UK and Twitter the parent company, while researching I just found PDFs of the company Modern Slavery Act not necessarily mentioned on the company websites.
Twitter UK is part of Twitter the parent company
https://www.business-humanrights.org/en/companies/twitter/?issue=359
The MSA Statement is found in the corporate governance section of the company's website. It is not easy to find. One must go to the investor relations page: https://investor.twitterinc.com/home/default.aspx