I don't think it's unlockable. You see I'm using an honor device (huawei basically)

I have an Android device with a locked bootloader and no available custom ROMS. Am I fucked ?

Here you go: https://www.apkmirror.com/apk/lineageos/lineage-os-phone/

The fossify dialer is good. If you want you can also try lineage os dialer.