After UEFI HTTP Boot was added to spec, HTTP support was added to the public Tianocore EDK2 tree. But initially there was no HTTPS support. Fast forward through a bunch of other branches and work, and now it looks like there’s nearly ready to have HTTPS in the EDK2 tree, given below patch. If you are using UEFI HTTP Boot withOUT httpS support, ask your vendor for an update!
Subject: [edk2] [Patch 0/2] Enable the HTTP switch
If the value of PcdHttpEnable is TRUE, HTTP is enabled. Both the “http://” and “https://” schemes are acceptable. Otherwise, HTTP is disabled. The “http://” scheme will be denied.