Thanks for your EFI ! I successfully installed 10.15.6 with it. But I noticed that touchpad, brightness do not work.
Following the patch instructions on https://www.tonycrapx86.com/threads/guide-hp-spectre-x360-13-ap0037tu-late-2018.295518/page-4#post-2153788 could solve these problems.
For the WIFI and bluetooth, thanks to https://github.com/OpenIntelWireless/itlwm https://github.com/OpenIntelWireless/HeliPort and https://github.com/OpenIntelWireless/IntelBluetoothFirmware , now built-in Wi-Fi and bluetooth work fine now. ( Airdrop and handoff are impossible )
I have uploaded my EFI on github: https://github.com/SeptemberHX/HP-Spectre-X360-13-late-2018-Hackintosh
Thanks for your EFI again.