Buy a used 1l mini PC like the Lenovo thinkcentre tiny (or similar Dell or HP models). You will have to spend a bit more, but you could get one with a pretty capable Intel CPU from gen 7 or 8 upwards for virtualization with Proxmox.
If you’re really just looking for a x86 SBC, get a Radxa with an Intel N100 or something similar. They sell at about your price limit with low specs on Aliexpress:
I’ve bought some refurbished 1l PCs in places where others might have bought RPi. Drawbacks are more energy consumption and, generally, no GPIO (at least built-in). Also bigger in size. I have one Lenovo M600 which has four serial ports (DB9) and one parallel port (DB25) on some kind of extension module. Because of the module it also has more space for cooler, thus making it passively cooled.
OS: Gentoo Linux x86_64 Host: 10GJS01G00 (ThinkCentre M600) Kernel: Linux 6.6.101-M600-minimal-0.1 Uptime: 1 day, 23 hours, 59 mins Packages: 567 (emerge) Shell: bash 5.2.37 Display (ACER H235HL): 1920x1080 @ 60 Hz in 23" [External] Terminal: tmux 3.5a CPU: Intel(R) Celeron(R) N3010 (2) @ 2.24 GHz GPU: Intel Atom/Celeron/Pentium Processor x5-E8000/J3xxx/N3xxx Integrated Graphics Controller @ 0.60 GHz [Integrated] Memory: 312.46 MiB / 7.37 GiB (4%) Swap: 0 B / 32.00 GiB (0%) Disk (/): 8.90 GiB / 19.94 GiB (45%) - xfs Disk (/var/cache/pkg): 4.41 GiB / 4.84 GiB (91%) - ext4Fast it ain’t, but does fit the bill.
one parallel port (DB25)
You might even be able to use the parallel port as basic GPIO, especially if it’s on the I/O bus and not some sort of PCI adapter.
For me an ABC is really a PCB with components on it à la RPI, I haven’t see a lot of x86 like that except industrial one and they are $$$.
Have you thought of a beelink mini PC? This one is $149… https://www.amazon.com/Beelink-Lake-N150-Upgraded-Computer-Business/dp/B0F3C6R47G
Do you want x86-64 (amd64) or arm64? Those are two very different things.
Devuan supports arm64.
Or, relax your SBC restriction and get a mini-pc board like a NUC or N100, or similar embedded system. Even an HDMI stick PC.
Nope. If you’re talking SOC, nothing like that exists anywhere near this price point. If you just mean a cheap x86 machine, find a used minipc or something on eBay, but it’s going to be a crapshoot.
I also hate systemd and use slackware and devuan, both of which works on aarch64. I believe Void also works but I never tried it.
USD $60 seems a bit low for an x86 SBC.
The cheapest SBC x86-64 I can find is LattePanda Delta. But it cost ~$200.
Have you tried MX Linux? It is based on Debian, they have a distro for RPI, and they have no systemd
