mac – Why doesn’t my dual boot (macOS/Linux Mint) iMac not boot after I deleted the Linux Mint partition?

I had a dual boot (macOS/Linux Mint) iMac (2017 27″) for about a year, recently my iMac has not enough space so I wanted to remove Linux Mint.

In disk utility, I delete a 7GB swap partition and a 20GB partition for sharing files and merged with the partition where Linux Mint 21 was installed.

After that, macOS can not boot.

I ran macOS recovery mode, in terminal I saw the drive info like this:

Disk0: 
0:GUID_partition_scheme                  *1.0 TB    disk0 
1:EFI EFI                                 209.7 MB  disk0s1 
2:FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF    841.7 GB  disk0s2 
3:Linux filesystem                        120 GB    disk0s3

The second one, disk0s2 with strange name FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF should be the partition where macOS is installed.

For reference I found a post here in Super User which is a little similar problem, unfortunately my knowledge of running codes in terminal is very poor.

I tried also in macOS internet recovery mode to reinstall macOS, but there is no disk for me to choose to install.

I reinstalled Linux Mint on this 120 GB partition, which runs well, unfortunately it’s impossible from there to access files in macOS partition which are my most concerns. Is there a way to access macOS files from Linux Mint or some other methods?

Is the disk0s2 partition repairable so the macOS will be able to boot?