[OnePlus 9 Pro] nrmh:
I tried flashing stock by running fastboot flashall on the output of the payload_dumper dump of the official firmware. Now I can't access the recovery or system, only fastboot.

Here's the output of fastboot -w:

Erasing 'userdata' OKAY [ 0.386s]

F2FS-tools: mkfs.f2fs Ver: 1.14.0 (2020-08-24)

Info: Disable heap-based policy
Info: Debug level = 1
Info: Trim is disabled
Info: Set conf for android
Info: Segments per section = 1
Info: Sections per zone = 1
Info: sector size = 512
Info: total sectors = 464059800 (226591 MB)
Info: zone aligned segment0 blkaddr: 512
Info: add quota type = 0 => 4
Info: add quota type = 1 => 5
[f2fs_init_sit_area: 587] Filling sit area at offset 0x00600000
[f2fs_init_nat_area: 621] Filling nat area at offset 0x01a00000
[f2fs_write_root_inode:1210] Writing root inode (hot node), 2b200 0 200 at offset 0x00176640
[f2fs_write_default_quota:1286] Writing quota data, at offset 0002b801, 0002b802
[f2fs_write_qf_inode:1377] Writing quota inode (hot node), 2b200 0 200 at offset 0x00176641
[f2fs_write_default_quota:1286] Writing quota data, at offset 0002b803, 0002b804
[f2fs_write_qf_inode:1377] Writing quota inode (hot node), 2b200 0 200 at offset 0x00176642
[f2fs_update_nat_root:1431] Writing nat root, at offset 0x00001a00
[f2fs_add_default_dentry_root:1628] Writing default dentry root, at offset 0x0002b800
Info: Overprovision ratio = 0.420%
Info: Overprovision segments = 956 (GC reserved = 484)
[f2fs_write_check_point_pack: 774] Writing main segments, cp at offset 0x00000200
[f2fs_write_check_point_pack: 911] Writing Segment summary for HOT/WARM/COLD_DATA, at offset 0x00000201
[f2fs_write_check_point_pack: 938] Writing Segment summary for HOT_NODE, at offset 0x00000202
[f2fs_write_check_point_pack: 950] Writing Segment summary for WARM_NODE, at offset 0x00000203
[f2fs_write_check_point_pack: 961] Writing Segment summary for COLD_NODE, at offset 0x00000204
[f2fs_write_check_point_pack: 969] Writing cp page2, at offset 0x00000205
[f2fs_write_check_point_pack: 989] Writing NAT bits pages, at offset 0x000003fe
[f2fs_write_check_point_pack:1010] Writing cp page 1 of checkpoint pack 2, at offset 0x00000400
[f2fs_write_check_point_pack:1029] Writing cp page 2 of checkpoint pack 2, at offset 0x00000405
[f2fs_write_super_block:1062] Writing super block, at offset 0x00000000
Info: format successful
Sending 'userdata' (85 KB) OKAY [ 0.005s]
Writing 'userdata' OKAY [ 0.004s]
Erasing 'metadata' OKAY [ 5.136s]
Erase successful, but not automatically formatting.
File system type raw not supported.
Finished. Total time: 6.587s

And here's the output of fastboot flashall:

--------------------------------------------
Bootloader Version...:
Baseband Version.....:
Serial Number........: 6af15dad
--------------------------------------------
android-info.txt syntax error: ECHO is on.
Setting current slot to 'a' OKAY [ 0.010s]
Sending 'boot_a' (196608 KB) OKAY [ 4.590s]
Writing 'boot_a' OKAY [ 0.540s]
Sending 'dtbo' (8192 KB) OKAY [ 0.204s]
Writing 'dtbo' OKAY [ 0.031s]
Sending 'vbmeta' (8 KB) OKAY [ 0.002s]
Writing 'vbmeta' OKAY [ 0.001s]
Sending 'vbmeta_system' (4 KB) OKAY [ 0.002s]
Writing 'vbmeta_system' OKAY [ 0.001s]
Sending 'vendor_boot' (98304 KB) OKAY [ 2.163s]
Writing 'vendor_boot' OKAY [ 0.290s]
Sending 'odm' (55656 KB) OKAY [ 1.377s]
Writing 'odm' FAILED (remote: '(odm_a) No such partition')
fastboot: error: Command failed

The reason it says syntax error: ECHO is on. is because I tried to make an empty file with echo > android-info.txt. I forgot that doesn't work.