Hello,

 

I'm looking to replace my x86 micro tower with a SBC, to mainly use it as a NAS and media player.

 

On the hardware side, I would like to have a native SATA port (for the NAS hard disk), HDMI output and H.265 decoding (media player), at least 4GB of RAM (to be somewhat future-proof). Bluetooth is a plus to play some retro games

Not sure about the OS storage: SD card, eMMC, an hard disk on another SATA port?

 

At the moment I found two boards: the Radxa Rock 3A (with its DIY SATA over USB cable) and Odroid HC4.

Both are supported by Armbian, but maybe there is a more recent board that I didn't find?

 

Thanks.

All depends on your budget.
The HC4 is a good option. I've got 2 of them that I use a NAS. 
Just no bt or wifi. That can be fixed with a bt dongle.
It is a nice device for gaming too. Not very powerful, but has good software.

I also use a NanoPi R6S (RK3588) with USB3 to SATA adapter with a 2TB SSD. That has 2.5GbE. So can do up to 280MB/s over my network. But software support ain't great (yet) for it.

The NanoPi R5S has a bit better I/O with NVMe. But is way less powerful.

There are also older SBCs with SATA like the Orange Pi + and OPi+2. Totally not powerful. But does the job of slow NAS. OPi+2 has gigabit ethernet while OPi+ only has 100Mbit. I used to use the OPi+2 for many years as NAS. Now happy to have replaced it with R6S.

Any SBC can do what you want with a USB3 to SATA adapter. Just see if it's got USB3.

I would probably look for an RK3399 since it's the best supported SoC with the best I/O.
NanoPi M4B for example has PCIe over GPIO on which you can put a 4 x SATA hat.
It does cost a bit more, but you get what you pay for. I used to use it with a NVMe hat as main desktop.
Now I use RK3588 for that goal. Mekotronics R58X-4G/RK58X-Pro. It has everything. NVMe, SATA, HDMI-out, DP-out, USB-C with DP, HDMI-in, wifi, bt, GPU drivers and VPU drivers. Great for gaming. It's is powerful, has great software. But doesn't have mainline support yet.
It is the most future proof. Rock5B I can't advice since there are a few design flaws on it.

I'm not sure about the Rock3A. I don't have it and am not sure if the software is good. I kind of lost my trust in Radxa for that. They make too many variations what makes supporting their boards near impossible.
Odroid's always have great software.
Check my youtube channel for more info. https://www.youtube.com/channel/UCpv7NFr0-9AB5xoklh3Snhg