thank you for its details
You're most welcome.
In case you do have some basic knowledge on software development then you can perhaps take a peek at the commit history on github here
https://github.com/aros-development-team/AROS/commits/masterIf you look closely you can see that for example the raspi just had some commits being made less than a day ago (i am assuming to try to fix some issues that presented itself during the build/testing or because it was already anticipated to address certain issues).
if it's brand new ...
It is not entirely brand new (see also my answer later), the raspi branch exist for a couple of years now.
What is new however, is that since the transition to a new updated abi (abiv1) it became clear that a) there still need to be done a lot of work on the raspi port and b) the AROS build-system in general needed an overhaul as well. Especially the latter required (and still requires) a lot of work.
Besides that, there was also a transition from svn to git(hub) and support for a new build-software (azure) was added as well.
In all that development violence and changes the raspi branch simply was left a bit behind the other branches (as the main branch is x86_64).
and as I'm not a developer, I don't see what I could bring to the developers in a bug report except that it doesn't boot on rapsberry pi 3 & pi400.
And, with all due respect, that is where you are a bit wrong
Developers rely on reports, just as you just did. They simply do not have the time to check each and every branch on a daily base and that is where us users come in and can help a bit.
The only "crime" you committed is that the build for the raspi branch just started working again, and as such developers keep an (closer) eye on things for a bit when such things happen. For detailed reports they really rely on the user-base.
So in case you can be bothered i would advise to keep an eye open on the progress and try for example once a week/month or so.
Even though you are perhaps not a developer, it is perfectly valid to ask such a question (on github or otherwise) how many more work is needed to be able to test the raspi branch or how long that would approximately take (i have currently no idea what needs to be done). If you have an github account then that would be the easiest way, otherwise you could use the developers slack-channel. Sometimes developers can also be found on the #aros irc channel at freenode.
afaik they do not have an account here or in case they do, do not react (often) in public threads here.
In case you do not wish to wait for the progress on the raspi branch, then there are alternatives as well.
For example, it is possible to run AROS hosted on your pi, see
http://www.aros.org/nightly.php (linux-armhf-system and linux-armhf-contrib) or in case you have a "powerful" enough computer which runs linux/windows you can use virtualization software like vmware/virtualbox (there are others as well) and run or install AROS there.
The latter isn't exactly the same experience as running AROS native but you can configure most (if not all) virtualization software in such a way that it integrates seamlessly with your OS. I had AROS running on virtualbox on my windows machine for years and am now doing the same on a linux machine. For development i use the hosted version of AROS because that works better for my personal work-flow.
As a sidenote, if you truly seek the a500 experience then you are probably better off using an emulator like fs-uae/winuae because they can emulate the Amiga to (almost) perfection. AROS is more geared towards users that like the experience of the operating system. AROS itself does not have any support for integration of running original Amiga software, but Icaros desktop does come with an emulator named janus-UAE and paolone tried to make that experience as seamless as he was able to make it (with support from the developer of Janus-UAE as well) but janus-UAE is showing its age
regards,