But - don’t be misled by the description Secure Boot - it is only secure in the sense that the firmware contains a signature which signals to the firmware - you my give over control to the loader signed with this signature.
It is possible - on some systems - to sign and enroll other efi loaders into the secure boot database.
See Unified Extensible Firmware Interface/Secure Boot - ArchWiki
An example of installing a Manjaro only encrypted system using Secure Boot
If you have the necessary knowledge, it can be modified for dual boot with e.g. Windows.