UPD: Volla phone (yggdrasil) is not a native-kernel linux device, it is a Lineage/android9/Halium device. Which is not bad after all, but my question below makes no sense then.
Hi,
that's very kind of you to let us download the kernel source, the thing is though it cannot be successfully build without a proper .config file in place.
Would you please be even more kind and provide this actual file or just a link to your live (and accessible) git repo!
Thanks in advance.