I ordered a new CCR2004-16G-2S+PC and it arrived with V7.3
I upgraded to latest stable (V7.3.1)
stuff just does not work right on this (sftp and firewall filtering on bridge with interface list).
I want to downgrade to V6 but cannot even get Etherboot to work.
I’ve followed all the procedures here https://wiki.mikrotik.com/wiki/Manual:Netinstall.
anyone done an Etherboot on that model?
You can not install version older than factory software.
You can see that version on System / Resources / Factory Software field.
When batches are produced, the latest version is often used, especially if some components, with the current components shortage,
are out of stock and in the old software versions there are no drivers or support for the new alternative hardware used.
The license is broken when you install a version older than ‘factory version’ too.
Since you can’t install it, what does it matter?
Where there is a will, there is a way? lol
That is how I know that the license breaks when one installs a version previous to the factory version..
Other people have (found a way to) installed a previous version.. Even if the drivers are there, you still have a broken system.
Some links 
?
https://openwrt.org/toh/mikrotik/rb941-2nd
It is possible to change device boot loader from the OpenWrt, e.g. to downgrade it for enabling serial access. There are 2 bootloaders in the board: routerboot2 (main loader) and routerboot (backup loader, on the beginning on the flash). I am recommending to experiment with the main (routerboot2) loader which is located on the mtd3 partition, because if it is damaged board can still be booted using routerboot. If routerboot is damaged you will have to reflash the memory chip using programmer. You can choose which loader to use using rbcfg tool or from the routeros menu. To force boot from the backup loader turn device on with button pressed and wait ~30 seconds.
To change the loader you will have to:
Download boot loader image from the vendor web site, use url like http://i.mt.lv/routerboard/files/qca9531L_3.27.fwf. First 32 bytes of the file is a header, which should be removed before flashing, e.g. using dd command: dd if=./qca9531L_3.27.fwf of=./routerboot-3.27 bs=4 skip=8.
Flash protection needs to be removed in the mach-rb941.c for the routerboot2 (or routerboot) partitions. Do backup of the partition first and flash your stripped boot loader using mtd tool.
Restart device, that's it :)
This post shows how to update to the latest 6.43.7 bootloader on rb-941-2nd-tc with the routeros interface
As far as I can see, it involves booting OpenWRT, using mtdtool, replacing routerboot or routerboot2 and praying the device boots afterwards, you can then downgrade the routeros version to match the earlier routerboot version.
Do not misunderstand factory/current RouterBOOT with factory software…
Already you can change bootloader, but the problem is (net)install or downgrade to previous versions prior to factory software.
Factory RouterBOOT do not count, Factory RouterBOOT limit only RouterBOOT, not RouterOS.
I have some updated later factory routerboot 6.37 but with factory software 6.30.2
I can install 6.30.2 without problem with factoru/current 6.37 routerboot.
But I can not install current routerboot older than 6.37 or routeros older than 6.30.2
So, do not depend on RouterBOOT, but for something wroten elsewhere…
I cannot even get the CCR2004-16G to netinstall. holding reset during boot never does anything. Tried on ports Eth1 and Eth16.
Simply does not work.
You try netinstall 6.x? I’ts normal, only netinstall 7.x can boot that device.
Or if not this, probably you not are able to run correctly netinstall (and sorry, I can not suppose why)
The third alternative can be only the hardware is broken, because I never lost on all this years,
form 2007, a device just for a wrong netinstall (at max I lost the licence one time, and another time the device see different platform on 4.x…)
My problem is not the version of netinstall i’m trying to use but the HW does not even go into the right mode. I never get a link light on any ethernet port.
Read para H. please. https://forum.mikrotik.com/viewtopic.php?t=182373
I just discovered KalTek’s youtube channel, which has 3 good MikroTik related videos; one that has “how NetInstall works in great and intricate detail”. I discovered the channel on Reddit, I don’t know if he has a MikroTik forum username or not (I can’t find KalTek with search on the forum). The videos are not short, but very thorough and presented well.
How Mikrotik Netinstall actually works
The other two videos (as of 2022-07-20) are
Mikrotik Bridge VLAN Filtering and Mikrotik Router on a stick overview
Use the serial console and the boot menu..
But there is a reason you can’t install a lower version that what it came with. Don’t try.