Werner

moved to csc
 
 
https://docs.armbian.com/User-Guide_FAQ/#why-no-universal-image
 
tl;dr: You are using the wrong image. Get/build one for your board

Yes. This is an example of a rk3588 based board of mine:
 
overlay_prefix=rockchip-rk3588 overlays=panthor-gpu opp-oc-24ghz The overlay names come from /boot/dtb/*/
find an overlay matching your soc and needs and enable by putting its name to overlays=. Then reboot. Having a serial console to read uboot logs can show if it has been loaded properly or in case it did not why.

moved since neither a review nor a tutorial.
 
I made a writeup just a few days ago how to get an idea about how Armbian puts its kernel and uboot sources together with an example for a different board: 
 

This device is community-maintained. Armbian core team does not monitor its status nor gets involved into development here. However anyone from the community can step up and send fixes.
 
I saw some stuff upstreamed from time to time for 5 ultra and max, hit somewhere between 6.16 and 6.18 I guess. When rockchip64 gets bumped further they will be available for these boards.
Since mainline is still under development though sticking with 6.1.y vendor kernel isn't a bad option since most things work here.
 
 
 

Tried this way? https://docs.armbian.com/User-Guide_Autoconfig/

https://docs.armbian.com/Process_Contribute/#adding-a-new-board

I don't think there are pre-built images with both ha and de by default. 
You can try to build your own by adding this extensions to your own userpatches and enable it: https://github.com/armbian/os/blob/main/userpatches/extensions/ha.sh
 
 

https://docs.armbian.com/User-Guide_Autoconfig/

This should have been addressed: https://github.com/armbian/linux-rockchip/pull/373
May take a while until an updated kernel is available via apt. You can always build a up-to-date package by yourself using the build framework.

Raspberry images are compatible from 3b up to 5b

Here are some:https://github.com/armbian/community/releases/

Maybe this helps? https://forum.armbian.com/topic/29427-shrink-backup-a-tool-for-backing-up-sbcs/

direct boot from nvme isn't possible. Boot loader (u-boot to say) must be present on SPI, eMMC or microSD.

Check here https://github.com/armbian/community/releases/tag/25.5.0-trunk.256
or on a mirror with archive https://docs.armbian.com/Mirrors/#current-mirrors
for what you are looking for. We're aware that some links are broken for yet to be determined reason.

There are for once some inconsistencies in terms of prefixes across various soc families and for the other configng isn't perfect (yet ).
Feel free to share your issue at its repository: https://github.com/armbian/configng/

fixed

Not sure if it is possible to use a local kernel source directory. At least I don't know how to do that. Easiest is probably just to create a repo and define url and branch in board your custom board config.

Yes, DB9 won't work.
But if, as eselarm mentions, a proper chip is on board already a simple usb-a to usb-c or c-to-c cable should do.
Check dmesg when connection to see what pops up.

Between days and month. Depending on time, issues, regressions,... 
Refrain from asking for ETA. Putting pressure on developers who give you something for free is abusive.

BOARD=uefi-x86

Install code { font-family: Consolas,"courier new"; color: crimson; background-color: rgba(0, 0, 0, 0.2); padding: 2px; font-size: 105%; } qemu-user-static package and retry

Try setting ZRAM_PERCENTAGE=50 where 50 would be half of available memory. Not sure if the builder picks this up.
If it doesn't I'd go the customize-image.sh route and use this to modify the /etc/default/armbian-zram-config file just before assembly closure.

No worries. Everyone here started small
edge and vendor are Armbian terms for kernel branches just like current.
You guessed correct, edge is bleeding edge and usually follows latest mainline kernel (6.14.y today).
vendor is based on Rockchip BSP kernel which is 6.1.y at the moment. While a bit out of date most hw functions work here.
current usually follows latest available LTS mainline kernel.
 
As you're a beginner and most likely just want things to work I suggest to try a vendor kernel based image first.

If a kernel package exists as artifact in oci cache it will be downloaded and used. Only if there is no artifact it will be built from scratch. After a new kernel version is released it may take a few days until oci catches up.
However once locally built it will also be cached locally so it will be re-used if you start another build.