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I first used Kingston endurance SD card with Armbian Buster image. This failed due some incompability with Odroid N2 UHS implementation, but Sandisk extreme SD card worked with same image.
After successful boot runned nand-sata-install to ADATA SP 550NS38 SSD connected using VL817 SATA Adaptor (2109:0715).
Upgraded the Debian to Bullseye and installed Mesa 21.2.0 packages from experimental repositories, arm64 firefox-esr and armhf Chromium via multiarch to use widevine extracted from ChromeOS images (local err.ee web broadcasts some programs with widevine encryption). This was in the end of august. It mostly worked, but had 3 weird problems that I think to have solved now having some free time.
 
The USB boot hanged up about half of times after kernel detected the SATA drive. Turns out that UAS is culprit, disabling UAS with usb-storage.quirks=2109:0715:u made it now boot every time without problems (modified /boot/boot.ini). About 2-3 minutes after boot the compositor froze (no matter which - tried Xorg compton, wayland Weston and Wayfire (self compiled). Turns out armbian has /etc/udev/rules.d/hdmi.rules which runs /usr/local/bin/hdmi-hotplug. For some reason the hdmi-hotplug script stalls on my Odroid installation and when systemd finally killed it, something went wrong and the compositors froze. Diverting the hdmi.rules fixed it. This was/is weirdest - when TV connected via HDMI was off and turned on, then sometimes the board would shutdown. Found from auth log "auth.log.1:Dec 25 19:04:59 piix systemd-logind[1641]: Power key pressed." Like WTF, i don't have any "power key" and why it gets invoked when TV is turned on. Set the *Key=ignore in /etc/systemd/logind.conf and it seems fine now, no idea what went wrong there. The kernel even don't have CEC enabled (CONFIG_CEC_MESON_AO and CONFIG_CEC_MESON_G12A_AO are not set for some reason in the armbian kernels).  
A bit later I also saw 5.15.8-meson64 kernel OOPS "Unable to handle kernel execute from non-executable memory" at regmap_update_bits_base+0x74/0x98, meson_clk_cpu_dyndiv_set_rate+0xf4/0x118. As I hadn't seen this before, downgraded to 5.13.12-meson64. I plan to report the OOPS with full kernel dmesg output, when I'll have a bit more time (probably the https://bugzilla.kernel.org/ would be right place?).
 
Currently it seems to work fine, with the 5.13.12-meson64 kernel and mesa/panfrost 21.2.1-2 (from snapshot.debian.org). Weston is used as Wayland compositor. It is important to note that I have 1080p TV, and all video decoding is done on CPU without using the Amlogic VPU acceleration, as the VPU driver is currently both broken in the kernel and unsupported in unpatched userspace. I expected this when choosing the board. Fortunately the 4xA73@2.4GHz is fast enough for decoding most 1080p videos and panfrost is fine for doing the video output after decoding. AFAIK playing 4K videos is currently not possible on Odroid N2 with mainline kernel and the vendors proprietary VPU decoder isn't supported by any software in open source distributions like Debian. Interesting is that Firefox seems to handle the video decoding pathway better for Youtube in this configuration,
while Chromium occasionally stutters on some Youtube videos, these seem to be fine with Firefox. Luckily this seems to not affect the site where I needed widevine (that works only with Chromium in practice). In september widevine upgraded to version needing patched libc. I got patched armhf libc6 package from apt.xbian.org repository.
 
The ALSA configuration is weird, amixer scontrols | wc gives 50 controls, and if misconfigured, then the thing doesn't give any audio output. I found the following script from somewhere that "fixes" it into working state:
 
amixer sset 'FRDDR_A SINK 1 SEL' 'OUT 1' amixer sset 'FRDDR_A SRC 1 EN' 'on' amixer sset 'TDMOUT_B SRC SEL' 'IN 0' amixer sset 'TOHDMITX I2S SRC' 'I2S B' amixer sset 'TOHDMITX' 'on' amixer sset 'FRDDR_B SINK 1 SEL' 'OUT 2' amixer sset 'FRDDR_B SRC 1 EN' 'on' amixer sset 'TDMOUT_C SRC SEL' 'IN 1' amixer sset 'TOACODEC SRC' 'I2S C' amixer sset 'TOACODEC OUT EN' 'on' amixer sset 'TOACODEC Lane Select' '0' amixer sset 'ACODEC' '255' amixer sset 'FRDDR_C SINK 1 SEL' 'OUT 3' amixer sset 'FRDDR_C SRC 1 EN' 'on' amixer sset 'SPDIFOUT SRC SEL' 'IN 2'  
After that ALSA pcm "hw:0,1" output works. I configured dmixed and removed pulseaudio, as it seemed to complicate things with no benefit when mpc and browser run as different users.
 
Armbian is great (couldn't have the board working so well without armbian) and merry holidays for you
Hoping this helps others having Odroid N2(+) board.