Seems GPT is now confused and corrupt - how do I recover my data?

Sun Oct 18 21:15:50 2020
Command line: TestDisk

TestDisk 7.1, Data Recovery Utility, July 2019
Christophe GRENIER <grenier@cgsecurity.org>
https://www.cgsecurity.org
OS: Linux, kernel 5.4.0-51-generic (#56-Ubuntu SMP Mon Oct 5 14:28:49 UTC 2020) x86_64
Compiler: GCC 9.2
ext2fs lib: 1.45.5, ntfs lib: libntfs-3g, reiserfs lib: none, ewf lib: none, curses lib: ncurses 6.1
User is not root!
Hard disk list


TestDisk exited normally.
Using locale 'en_GB.UTF-8'.


Sun Oct 18 21:15:54 2020
Command line: TestDisk /debug

TestDisk 7.1, Data Recovery Utility, July 2019
Christophe GRENIER <grenier@cgsecurity.org>
https://www.cgsecurity.org
OS: Linux, kernel 5.4.0-51-generic (#56-Ubuntu SMP Mon Oct 5 14:28:49 UTC 2020) x86_64
Compiler: GCC 9.2
ext2fs lib: 1.45.5, ntfs lib: libntfs-3g, reiserfs lib: none, ewf lib: none, curses lib: ncurses 6.1
/dev/sda: LBA, HPA, LBA48, DCO support
/dev/sda: size       500118192 sectors
/dev/sda: user_max   500118192 sectors
/dev/sda: native_max 500118192 sectors
/dev/sdb: LBA, HPA, LBA48, DCO support
/dev/sdb: size       2000409264 sectors
/dev/sdb: user_max   2000409264 sectors
/dev/sdb: native_max 2000409264 sectors
Warning: can't get size for Disk /dev/mapper/control - 0 B - 0 sectors, sector size=512
Warning: can't get size for Disk /dev/loop9 - 0 B - 0 sectors, sector size=512
Hard disk list
Disk /dev/sda - 256 GB / 238 GiB - CHS 31130 255 63, sector size=512 - C300-CTFDDAC256MAG, S/N:0000000010490300653F, FW:0006
Disk /dev/sdb - 1024 GB / 953 GiB - CHS 124519 255 63, sector size=512 - Samsung SSD 860 PRO 1TB, S/N:S42NNX0N500045F, FW:RVM02B6Q
Disk /dev/sdc - 31 GB / 29 GiB - CHS 29856 64 32, sector size=512 - SanDisk Ultra, FW:1.00
Disk /dev/loop0 - 267 MB / 255 MiB - 523400 sectors (RO), sector size=512
Disk /dev/loop1 - 58 MB / 55 MiB - 113296 sectors (RO), sector size=512
Disk /dev/loop2 - 57 MB / 54 MiB - 112552 sectors (RO), sector size=512
Disk /dev/loop3 - 31 MB / 29 MiB - 61200 sectors (RO), sector size=512
Disk /dev/loop4 - 53 MB / 50 MiB - 103776 sectors (RO), sector size=512
Disk /dev/loop5 - 228 MB / 217 MiB - 446248 sectors (RO), sector size=512
Disk /dev/loop6 - 65 MB / 62 MiB - 127160 sectors (RO), sector size=512
Disk /dev/loop7 - 32 MB / 30 MiB - 63344 sectors (RO), sector size=512
Disk /dev/loop8 - 52 MB / 49 MiB - 101960 sectors (RO), sector size=512

Partition table type (auto): EFI GPT
Disk /dev/sdb - 1024 GB / 953 GiB - Samsung SSD 860 PRO 1TB
Partition table type: EFI GPT

Analyse Disk /dev/sdb - 1024 GB / 953 GiB - CHS 124519 255 63
hdr_size=92
hdr_lba_self=1
hdr_lba_alt=2000409263 (expected 2000409263)
hdr_lba_start=34
hdr_lba_end=2000409230
hdr_lba_table=2
hdr_entries=128
hdr_entsz=128
Current partition structure:
 1 P EFI System                    40     409639     409600 [EFI System Partition]
 2 P Mac HFS                   470911 2000208350 1999737440

search_part()
Disk /dev/sdb - 1024 GB / 953 GiB - CHS 124519 255 63
FAT32 at 0/0/41
check_FAT: Unusual media descriptor (0xf0!=0xf8)
FAT1 : 32-3182
FAT2 : 3183-6333
start_rootdir : 6334 root cluster : 2
Data : 6334-409599
sectors : 409600
cluster_size : 1
no_of_cluster : 403266 (2 - 403267)
fat_length 3151 calculated 3151
FAT differs, FAT sectors=0-16/3151
heads/cylinder 16 (FAT) != 255 (HD)
sect/track 32 (FAT) != 63 (HD)
set_FAT_info: name from BS used

FAT32 at 0/0/41
     EFI System                    40     409639     409600 [EFI System Partition] [EFI]
     FAT32, blocksize=512, 209 MB / 200 MiB

HFS+ magic value at 29/79/50
part_size 1999737440
     Mac HFS                   470911 2000208350 1999737440
     HFS+ blocksize=4096, 1023 GB / 953 GiB

HFS+ magic value at 124519/182/20
part_size 262144
     Mac HFS               2000409220 2000671363     262144
     HFS+ blocksize=4096, 134 MB / 128 MiB
This partition ends after the disk limits. (start=2000409220, size=262144, end=2000671363, disk end=2000409264)

HFS+ magic value at 124519/182/22
part_size 262144
     Mac HFS               2000147080 2000409223     262144
     HFS+ found using backup sector!, 134 MB / 128 MiB
Disk /dev/sdb - 1024 GB / 953 GiB - CHS 124519 255 63
Check the harddisk size: HD jumper settings, BIOS detection...
The harddisk (1024 GB / 953 GiB) seems too small! (< 1024 GB / 953 GiB)
The following partition can't be recovered:
     Mac HFS               2000409220 2000671363     262144
     HFS+ blocksize=4096, 134 MB / 128 MiB

Results
   P EFI System                    40     409639     409600 [EFI System Partition] [EFI]
     FAT32, blocksize=512, 209 MB / 200 MiB
     Mac HFS                   470911 2000208350 1999737440
     HFS+ blocksize=4096, 1023 GB / 953 GiB
     Mac HFS               2000147080 2000409223     262144
     HFS+ found using backup sector!, 134 MB / 128 MiB

Hint for advanced users: dmsetup may be used if you prefer to avoid rewriting the partition table for the moment:
echo "0 409600 linear /dev/sdb 40" | dmsetup create test0
echo "0 1999737440 linear /dev/sdb 470911" | dmsetup create test1
echo "0 262144 linear /dev/sdb 2000147080" | dmsetup create test2

   P Mac HFS                   470911 2000208350 1999737440
     HFS+ blocksize=4096, 1023 GB / 953 GiB
Support for this filesystem hasn't been implemented.

interface_write()
 1 P EFI System                    40     409639     409600 [EFI System Partition] [EFI]
 2 P Mac HFS                   470911 2000208350 1999737440
write!
No extended partition
You will have to reboot for the change to take effect.