Firmware

General_IPC-HX5X3X-Rhea_Eng_N_Stream3_V2.622.0000000.18.R.20171110.bin

ENS Security firmware released Nov 10, 2017. May work with 270 devices, including IPC-EB5531, IPC-EB5531-AS, IPC-EB5531-M.

Download

Permanent copy on the Internet Archive (item page)

Hardware IDs this firmware's installer accepts (270 devices).

Where these IDs come from

Install: the installer's device list (board families), 5 IDs, vendor General (not counted: a more specific list exists)
check.img: the device's own hardware check list, 270 IDs

Read from inside the firmware (dahua package (zip variant)).

Flash layout: 16 partitions, 9 written by this firmware

From the firmware's partition table (partitionV2.txt).

Partition	Start	End	Size	Image	Filesystem	Built
MinBoot	0x0	0x40000	256.0 KB	dhboot-min.bin.img	—	2017-11-10
U-Boot	0x80000	0xc0000	256.0 KB	dhboot.bin.img	—	2017-11-10
hwid	0xc0000	0xe0000	128.0 KB	not written	—	—
partition(ro)	0xe0000	0xf0000	64.0 KB	partition-x.cramfs.img	cramfs	2017-11-10
Kernel	0xf0000	0x270000	1.5 MB	kernel.img	—	2017-11-10
romfs(ro)	0x270000	0x3c0000	1.3 MB	romfs-x.squashfs.img	squashfs	2017-11-10
web(ro)	0x3c0000	0xa40000	6.5 MB	web-x.squashfs.img	squashfs	2017-11-10
user(ro)	0xa40000	0x1a70000	16.2 MB	user-x.squashfs.img	squashfs	2017-11-10
updateflag	0x1a70000	0x1aa0000	192.0 KB	not written	—	—
config	0x1aa0000	0x1b10000	448.0 KB	not written	jffs2	—
product(ro)	0x1b10000	0x1b20000	64.0 KB	pd-x.squashfs.img	squashfs	2017-11-10
custom(ro)	0x1b20000	0x1b40000	128.0 KB	custom-x.squashfs.img	squashfs	2017-11-10
backupker(ro)	0x1b40000	0x1c20000	896.0 KB	not written	squashfs	—
backupfs(ro)	0x1c20000	0x1c70000	320.0 KB	not written	squashfs	—
data	0x1c70000	0x1d70000	1.0 MB	not written	jffs2	—
user1(ro)	0x1d70000	0x2000000	2.6 MB	not written	squashfs	—

Other files for much of the same hardware, from any vendor.