How to change the file system of a disk partition on a Mac while saving the files?

Question

macOS

In general, the situation is this: the Macbook does not want to boot from the main partition where my poppy axis is installed and all the files there. As it turned out, because the file system is unknown. Before that, I chemized with the installation of Linux. But the file system of a disk partition could not change without erasing this disk.

Turns out she could...

How to change the filesystem of a larger partition from "unknown" to "apfs"?

Answer 1

Could.
But not the file system, but the mark on the volume.
Boot from a Linux LiveCD and use fdisk to change the partition type to APFS.
It's easy to google.