The U.S. Army has an education site that provides pre-testing and individualized lessons based on the results of those tests.  The ACT is one of the learning courses they offer.  You do need to create a free account.  Click on the ACT Online Course for more information.

This page provides several resources from ACT including both printed and online practice tests for each subject area.  It also provides the official “Test Prep Guide 2021-22”, which contains information about ACT test dates, fee waivers, and test prep.

When you set aside four hours for an ACT practice test, it's important to try to get the most out of your time and energy. This site presents five critical tips as you take your ACT test that can help you prepare more effectively for test day.

With a wide variety of tests available, by selecting ACT, the user can access over 1300 practice tests for the ACT.  The online versions will provide the user with a detailed report once the test is complete.  This report includes several categories including important information such as “Concept Area” (with breakdown data), detailed “Explanations” for each question, and “Time per Question”.