In Android 11, to install a CA certificate, users need to manually:
Open settings.
Go to 'Security' or 'Password & security'.
Go to 'Encryption & Credentials'.
Go to 'Install from storage'.
Select 'CA Certificate' from the list of types available.
Accept the warning message (install anyway).
Browse to the certificate file on the device and open it.
Confirm the certificate install.
OR
Open settings
In the search box, search for cert
Select 'CA Certificate'.
Select 'CA Certificate' again.
Accept the warning message (install anyway).
Browse to the certificate file on the device and open it, usually it will be in your downloads folder..
Confirm the certificate install.
OR
Open settings
In the search box, search for install certificate from storage
Select 'Install certificates from storage'.
Select 'Install certificates from storage'. again
Select 'CA certificate' from the install a certificate menu.
Accept the warning message.
Browse to the certificate file on the device and open it, usually it will be in your downloads folder..
Confirm the certificate install.