The servers are using the new path:
IIS 10, Windows 2019 Core
"Let’s Encrypt Modern Chain (May not support some older devices)
This Let’s Encrypt chain uses the newer ISRG Root X1 root, which is trusted by current operating systems. This chain may cause issues for some old devices, particularly Android 7.0 and lower."
But Chrome on Android 8, 9, 10, 11 are giving me the “Your Connection is not secure”