The description for PlayIntegrityFix_v13 says "If you are using xiaomi.eu custom ROM expect to fail all tests."I installed Magisk v26.4 and PlayIntegrityFix_v13 directly from the links on the tutorial. I did not get any error when installing them.
They updated PlayIntegrityFix to a version 13.1 that does not have this description and my phone uses that and passed most checks. Maybe try that one instead?