OpenWrt does not contain a bootloader (except x86_64, as I recall).
I thought all MikroTik instructions included serial procedures, perhaps I'm wrong.
So how routers boot? Is it like "expect to find some stuff to run at xxxxxx address and just run it" (or "expect to find something on that storage chip")? If so, does that address change for every router or is it kinda standard? also in this case why would there be a different target just for mikrotik devices (for example on ar71xx)?
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Routers are (so far still) embedded devices, so it depends - there is not much of a standard at all. In general OpenWrt leaves the OEM bootloader (e.g. u-boot, CFE, redboot, etc.) untouched and gets booted by the existing vendor boot infrastructure (this only differs for x86 (grub) or devboards/ SBCs like e.g. sunxi (u-boot)).
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i see, so it means that "grub" (looking at pc side of things) will stay untouched, what changes is just the system itself (so everything outside of "/boot")?
OpenWrt always provides kernel and rootfs/ userland, while technically incorrect, you can consider the kernel to be 'chainloaded' by the OEM bootloader. There typically is no /boot/ on most routers, the kernel usually is written (raw) to a dedicated partition, there usually is no initramfs nor any bootloader components in /boot/.
Again, while similar, this is quite different to the heavily standardized boot process on more traditional PC-like platforms (or SBCs/ devboards).
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Got it 
Now problem with getting a working image and getting help is that if i post here compile logs they might not be useful because i have "heavily" modified the makefiles, should i post logs even though i'm not using the "official" build makefiles?
EDIT: Here is the link for the compile log https://ptpb.pw/P4zb ("warning" the file is 13mb +- i ran "make -j1 V=sc &> log")
Here i am again, has anyone looked at the log? i still can't figure why owrt isn't compiling 
Changes i made to makefiles:
Copied mikrotik folder from ar71xx to ipq40xx.
Changed every "Default" in ipq40xx/mikrotik/profiles/00-default.mk to "Default1" (so it would not conflict with existing "Default" profile).
Changed every "ATH79" to "IPQ40xx" in ipq40xx/mikrotik/config-default (maybe this is useless because those resulting compile flags do not exist).
Copied ar71xx/image/mikrotik.mk to ipq40xx/image/mikrotik.mk.
Changed "Default" to "Default1" in ipq40xx/image/mikrotik.mk
(I think this was all)
It would be really nice to have this AP supported
What are you doing?
It cant and it wontt work that way
I don't even know
i'm trying to somehow make a useable image, there is too little i know to be able to do this myself, i'm just messing around with files, copying stuff from here and there and hoping that this somehow will work (which it will not, that's why i'm looking for help )
Please dont try to flash it even if it somehow compiles.
There is no way to make a usable image that way.
How much does one of these cost?
about 45€, but there is not much worry into breaking it cause, from what i understood, it has a system similar to androids fastboot, it just boots the image, then after the image is booted and i got a connection there is the possibility to flash.
adding
LOADER_TYPE := elf
KERNEL := kernel-bin | loader-kernel
to the existing Makefile ipq40xx "define Device/Default" gives the same .elf which boots (at least it does not "crash" and go back to mikrotik's firmware) but has absolutely no conectivity. The ethernet led blinks though
Ughh, I thought about getting one of these new IPQ40xx Mikrotik devices but I cant justify them on a student budget.
Well, off course you dont get any connectivity as nothing is configured
@robimarko Were are you from, maybe i can donate one, if shipping is not going to cost more than the device...
ps: In the next days i will get one "hap ac2" to play with probaly.
From Croatia, good thing is that getting one from this platform to work will automatically enable getting all of the other Mikrotik devices using this platform to be easily supported.
This work can only be done on IPQ40xx Mikrotik device that has a serial port advertised on its product page.
Because otherwise there is no way to know where is it stuck as Mikrotik ships other ones without serial support being compiled at all into RouterBoot.
So, I think that only one that has serial is RB450Gx4:
That one is quite expesive, but for the specs it is understandable it seems like a good SBC server
Problem with this sxtsq 5 ac is that it seems ultrasonic welded, not sure how to confirm that without breaking everything. I doubt that it does not have a serial port somewhere in there
It most likely like every other Mikrotik device have serial header on the board but it is disabled by the bootloader
btw, what do you mean with
Well, off course you dont get any connectivity as nothing is configured
Do you mean configured on owrt? if so it might be possible to configure before compilation, no?
Also, here it says that
When rebooting a RouterBoard the bootloader (RouterBOOT) will always use the serial console (serial0 on RouterBoards) to send out some startup messages and offer access to the RouterBOOT menu.
So at least the bootloader outputs to the serial port on every routerboard devices (read all mikrotik devices)
Off course you have to preconfigure everything.
That is taken from the Wiki and it is not correct at all.
I can guarantee you that UART does not work on any never(As in 1-2 years old) device that does not adverise UART
sorry to bother again, is there any news on this?
Here some more info to better understand the device
Internal Photos
https://fccid.io/TV7LHG5ACD/Internal-Photos/Internal-photos-3620773.pdf
External Photos (maybe where to open it)
https://fccid.io/TV7LHG5ACD/External-Photos/External-photos-3620772.pdf
The serial console is most likely disabled by default
Some old notes how to enable it
https://oldwiki.archive.openwrt.org/toh/mikrotik/rb941_2nd#how_to_enable_serial_port
Uses same pintout (RX, TX, GND) ?