Single band, in EU look for a TL-WR842N v3 (EU). I think these are (or were) only sold in the EU and were relatively cheap. This is one of the fuller models among the entry level TP-Links-- it has Atheros chip, 16+64 memory, and USB.
My current favorite model is the Netgear R6100. Don't be put off by the internal antennas, it has very good radio performance that is comparable or better than most external antenna routers.
What about Archer C20i
seam to be supported...
https://lede-project.org/toh/hwdata/tp-link/tp-link_archer_c20i_ac750_v1
but some had trouble with it
EDIT:
Seams to be quite well covered in OpenWRT Wiki
https://wiki.openwrt.org/toh/tp-link/archer-c20i
What do you think of it ?
Cons:
70 euros from ebay Germany.
The TP-Link Archer C59 might come close to your requirements (starting around ~35 EUR, concurrent dual-band, 100 MBit/s ethernet), although I would recommend against buying non-GBit/s ethernet devices these days. Flashing is said to require tftp, but should be rather straight forward.
Disclaimer: I haven't tested this device myself.
looks like a satellite lol
Yes I can get it on Amazon for 35 euros but OpenWRT wiki says WIFI 5GHz broken and 2.4 is very bad... So it's a no go for now... Too bad it's a good device on paper.
Ar300m seams a good product I've found one for 46 euros on Amazon
What's the difference between nand and nor support ?
TP Link TL-WR810N V1.0 seams pretty close ?
NAND is not available in LEDE, but there are precompiled "clean" versions (no GL.inet GUI) for NAND and NOR memory available from the GL,inet downloads site. I think there are also tools to roll your own, but it's not something I do.
There is a dual external antenna version available from the GL.inet store, not sure about your market.
Thats old info, also the forum discussion is half a year old. Wifi is fixed in latest snaps. (Archer C59)
For which device ?
Why is nobody recommending the D-Link DIR-860L rev. B1?
Dual-band and dual-radio 802.11ac, gigabit Ethernet, USB 3.0, and it's available on Amazon as well, although (like everywhere) you'd need to check whether it's rev B they're carrying.
Granted, it's not 35 €, but in that price bracket you won't find a dual-radio 802.11ac router, let alone one with gigabit and USB 3. Reality check 
.
At that price you can find ARM-based devices (new and refurbs) that performs better....
raspberry pi's work great, does the raspberry pi 3 have gb networking now?
The Pi3 is not ideal for networking. Everything in or out of the CPU is bottlenecked through one USB2 port. Also the wifi chip is 2.4 only, Broadcom, with 1x1 tiny antenna.
guess ill rule that out and just use an raspberry pis as an mpi cluster and 2 new pci antennas on a desktop server or something.you can buy boards for multiple lan hubs btw.
Which ARM based device can you find at that price that performs better (including throughput and WIFI performance) ?
Yes it is: WRT1200AC, WRT1900ACS, WRT3200ACM
Those last 2 also have the strongest CPU performance you'll find in consumer grade routers on the market today.
I own them myself and although competition can handle 30/60Mbps highest encryption standard on consumer grade routers (everything up to 500 USD I consider consumer grade) the WRT3200ACM I get 120Mbps over VPN with highest encryption standards.
Note:'intel cpu with AES support can do 300Mbps without a fuss. So you might if you want real powerful hardware
just buy a cheap G4560 from intel which supports 4 threads on 2 cores and has a very high single thread performance
although very cheap and AES support. You run linux or whatever (i have windows 2012R2 servers) and than using oracle virtualBox and run lede on it as virtual router (use 2 NIC please - 1 for the WAN and 1 for the LAN) can do it with 1 NIC as well and use some virtualizing but 2 NIC I figured is the easiest..
Behind the LAN nic you put a 24 port 10Gbps switch and you'll have the most powerful router with 10Gbps internal LAN
capable of handling at least 10Gbps WAN and 10Gbps LAN and at least 300Mbps over VPN with highest encryption standards.
Make sure your NIC support 10Gbps as well to be future proof.
Look for refurbs on the WRT1***-series except WRT1900v1 which is using different (older) hardware for instance.
how high is your budget?
I have a 1200 but I'm looking for cheaper device