Base boot log here here and here
We can conclude that Flash is made like this:
| Place | MTD | Size | erasesize | Name |
|---|---|---|---|---|
| 0x00000000-0x00080000 | mtd0 | 00080000 | 00010000 | "u-boot" |
| 0x00080000-0x000c0000 | mtd1 | 00040000 | 00010000 | "u-boot-env" (1) |
| 0x000c0000-0x00100000 | mtd2 | 00040000 | 00010000 | "board-name" |
| 0x00100000-0x00e80000 (encapsulated 4 and 5) |
mtd3 | 00d80000 | 00010000 | "firmware" |
| 0x00100000-0x00280000 | mtd4 | 00320000 | 00010000 | "kernel" |
| 0x00280000-0x00e80000 | mtd5 | 00a60000 | 00010000 | "rootfs" |
| 0x005f0000-0x00d80000 | mtd6 | 007b0000 | 00010000 | "rootfs_data" |
| 0x00e80000-0x01000000 | mtd7 | 00180000 | 00010000 | "kernel2" |
| 0x01000000-0x01040000 | mtd8 | 00040000 | 00010000 | "sysinfo" |
| 0x01040000-0x01c40000 | mtd9 | 00c00000 | 00010000 | "rootfs2" |
| 0x01c40000-0x02000000 | mtd10 | 003c0000 | 00010000 | "jffs2" |
So we can write RawMTD save directly to flash like this:
Firmware (mtd3 Firmware = mtd4 kernel + mtd5 Rootfs)
tftpboot 0x8f00000 RawMTD/DGS-1210-28MP.mtd3.bin
sf update 0x8f00000 100000 d80000
OR
tftpboot 0x8f00000 RawMTD/DGS-1210-28MP.mtd4.bin
sf update 0x8f00000 100000 0x320000
tftpboot 0x8f00000 RawMTD/DGS-1210-28MP.mtd5.bin
sf update 0x8f00000 280000 0xa60000
Firmware 2 ( mtd4 kernel2 + mtd5 Rootfs2)
tftpboot 0x8f00000 RawMTD/DGS-1210-28MP.mtd7.bin
sf update 0x8f00000 0xe80000 0x00180000
tftpboot 0x8f00000 RawMTD/DGS-1210-28MP.mtd9.bin
sf update 0x8f00000 1040000 0x00c00000
And you want both firmware equal
tftpboot 0x8f00000 RawMTD/DGS-1210-28MP.mtd3.bin
sf update 0x8f00000 0xe80000 0xd80000
MTD6 "rootfs_data"
tftpboot 0x8f00000 RawMTD/DGS-1210-28MP.mtd6.bin
sf update 0x8f00000 5f0000 0x7b0000
MTD10 "jffs2"
tftpboot 0x8f00000 RawMTD/DGS-1210-28MP.mtd10.bin
sf update 0x8f00000 0x1c40000 0x003c0000
Why not MTD0 u-boot and MTD1 u-boot-env. I'am stuck in u-boot, I will not crash my last chance to save it 
Test
I tried to write on MTD3:
- stock rom (without first 0x40 bytes)
- openwrt (kernel, factory, sysupgrade)
- my MTD3 Save
No thing boot correctly. strange...
So i write, read back an check...
I fact 'sf write' didn't write, that why I put update on the exemple before, we have to update... It' longer but it works
u-boot># tftpboot 0x8f00000 RawMTD/DGS-1210-28MP.mtd3.bin
Using rtl8380#0 device
TFTP from server 192.168.1.66; our IP address is 192.168.1.132
Filename 'RawMTD/DGS-1210-28MP.mtd3.bin'.
Load address: 0x8f00000
Loading: Got ARP REPLY, mac addr (b4:b5:2f:b1:c2:fd), ip addr (192.168.1.66)
#################################################################
#######################################################
done
Bytes transferred = 14155776 (d80000 hex)
u-boot># iminfo 0x8f00000
## Checking Image at 08f00000 ...
Legacy image found
Image Name: OpenWrt
Created: 2024-03-22 22:09:42 UTC
Image Type: MIPS Linux Kernel Image (gzip compressed)
Data Size: 3236735 Bytes = 3.1 MB
Load Address: 80100000
Entry Point: 80100000
Verifying Checksum ... OK
u-boot># md 08f00000
08f00000: 27051956 ffffffff 65fe01a6 0031637f '..V....e....1c.
08f00010: 80100000 80100000 bff89088 05050201 ................
08f00020: 4f70656e 57727400 00000000 43414d45 OpenWrt.....CAME
08f00030: 4f544147 00000001 000010c1 80905a19 OTAG..........Z.
08f00040: 1f8b0800 00000000 02ffec7d 7d7c1c57 ...........}}|.W
08f00050: 79eebbb3 b3d2da5e ac91b456 16478946 y......^...V.G.F
08f00060: d68cb4a9 05ac1d83 55d83693 95ec3821 ........U.6...8!
08f00070: 80933a25 5ff4ee95 e460d350 9c105a97 ..:%_....`.P..Z.
08f00080: 08b395e4 209a8d46 37b88d49 dcb29525 .... ..F7..I...%
08f00090: dbd0b5d6 b40ab86d 02c20e89 29d01af3 .......m....)...
08f000a0: 715d0860 12830d24 d4400a86 2899fb3c q].`...$.@..(..<
08f000b0: f3618d15 d9847b6f ff28b57f bff59939 .a....{o.(.....9
08f000c0: 1feff779 cf7bce9c 73146f7c d51f49e8 ...y.{..s.o|..I.
08f000d0: 5fdba3ce 5129a4cd cac72559 d9275ab6 _...Q)....%Y.'Z.
08f000e0: b6b0450a 0533ab16 ee3006df 7a57e5d3 ..E..3...0..zW..
08f000f0: 6254fe5e 1a2b7f27 a9caa4e8 89d8fbef bT.^.+.'........
u-boot># sf write 0x8f00000 0x100000 d80000
u-boot># sf read 0x8f00000 0x100000 d80000
u-boot># iminfo 0x8f00000
## Checking Image at 08f00000 ...
Legacy image found
Bad Header Checksum
u-boot># md 08f00000
08f00000: 27051956 138cde24 65520002 0021427c '..V...$eR...!B|
08f00010: 80100000 80100000 a1009000 05050201 ................
08f00020: 4d404042 00427000 00000000 00404944 M@@B.Bp......@ID
08f00030: 45500105 00000000 00001000 00000000 EP..............
08f00040: 1f8b0800 00000000 02ffec7d 7d781c57 ...........}}x.W
08f00050: 79eebbb3 b3d2da16 84001002 12438946 y............C.F
08f00060: d6082089 05081902 01901481 00640820 .. ..........d.
08f00070: 00932225 5ff4ea91 e460d350 18001096 .."%_....`.P....
08f00080: 008085a4 00120402 37980008 d8220501 ........7...."..
08f00090: 12d0b5d6 b40aa025 00020a89 09c00871 .......%.......q
08f000a0: 01490040 10800000 00000804 0098c83c .I.@...........<
08f000b0: f1608114 09800967 de289156 3e949119 .`.....g.(.V>...
08f000c0: 190fe771 494b4a8c 1010046c 50150920 ...qIKJ....lP..
08f000d0: 528ba1c2 40012044 88c22501 51010a06 R...@. D..%.Q...
08f000e0: a6a0400a 04020206 2e100086 5a5645c1 ..@.........ZVE.
08f000f0: 02002a5e 02091527 80402440 8898c007 ..*^...'.@$@....
u-boot># sf update 0x8f00000 0x100000 d80000
u-boot># sf read 0x8f00000 0x100000 d80000
u-boot># iminfo 0x8f00000
## Checking Image at 08f00000 ...
Legacy image found
Image Name: OpenWrt
Created: 2024-03-22 22:09:42 UTC
Image Type: MIPS Linux Kernel Image (gzip compressed)
Data Size: 3236735 Bytes = 3.1 MB
Load Address: 80100000
Entry Point: 80100000
Verifying Checksum ... OK
u-boot># md 08f00000
08f00000: 27051956 ffffffff 65fe01a6 0031637f '..V....e....1c.
08f00010: 80100000 80100000 bff89088 05050201 ................
08f00020: 4f70656e 57727400 00000000 43414d45 OpenWrt.....CAME
08f00030: 4f544147 00000001 000010c1 80905a19 OTAG..........Z.
08f00040: 1f8b0800 00000000 02ffec7d 7d7c1c57 ...........}}|.W
08f00050: 79eebbb3 b3d2da5e ac91b456 16478946 y......^...V.G.F
08f00060: d68cb4a9 05ac1d83 55d83693 95ec3821 ........U.6...8!
08f00070: 80933a25 5ff4ee95 e460d350 9c105a97 ..:%_....`.P..Z.
08f00080: 08b395e4 209a8d46 37b88d49 dcb29525 .... ..F7..I...%
08f00090: dbd0b5d6 b40ab86d 02c20e89 29d01af3 .......m....)...
08f000a0: 715d0860 12830d24 d4400a86 2899fb3c q].`...$.@..(..<
08f000b0: f3618d15 d9847b6f ff28b57f bff59939 .a....{o.(.....9
08f000c0: 1feff779 cf7bce9c 73146f7c d51f49e8 ...y.{..s.o|..I.
08f000d0: 5fdba3ce 5129a4cd cac72559 d9275ab6 _...Q)....%Y.'Z.
08f000e0: b6b0450a 0533ab16 ee3006df 7a57e5d3 ..E..3...0..zW..
08f000f0: 6254fe5e 1a2b7f27 a9caa4e8 89d8fbef bT.^.+.'.......
To finish, you can push a stock image like this:
(do not forget to strip 64 = 0x40 bytes, and to adapt a62410 with the size returned by tftpboot)
tftpboot 0x8f00000 DGS-1210-FX-SERIES-FX-6-20-B020.hex
sf update 0x8f00000 0xe80000 0xa62410
reset
u-boot># iminfo
## Checking Image at b4100000 ...
Legacy image found
Image Name: OpenWrt
Created: 2024-03-22 22:09:42 UTC
Image Type: MIPS Linux Kernel Image (gzip compressed)
Data Size: 3236735 Bytes = 3.1 MB
Load Address: 80100000
Entry Point: 80100000
Verifying Checksum ... OK
u-boot># iminfo 0xb4e80000
## Checking Image at b4e80000 ...
Legacy image found
Image Name:
Created: 2021-09-17 9:50:05 UTC
Image Type: MIPS Linux Kernel Image (gzip compressed)
Data Size: 1035509 Bytes = 1011.2 KB
Load Address: 80000000
Entry Point: 80262000
Verifying Checksum ... OK
and folow baseline to chose on which you want to boot
PS: it was a three days no sleep challenge...