Cannot flash Lede 18 to TP-Link Archer C50v3 using U Tftp


I'm trying to flash LEDE 18 on my (stock) TP-Link Archer c50 v3.
I found the following procedure:
The only way to flash LEDE image in ArcherC50v3 is to use
tftp recovery mode in U-Boot:

  1. Configure PC with static IP and tftp server.
    2: em1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 00:26:18:21:db:08 brd ff:ff:ff:ff:ff:ff
    inet brd scope global em1
    valid_lft forever preferred_lft forever
    inet6 fe80::226:18ff:fe21:db08/64 scope link
    valid_lft forever preferred_lft forever
    ==> OK

  2. Rename "openwrt-ramips-mt7628-ArcherC50v3-squashfs-tftp-recovery.bin"
    to "tp_recovery.bin" and place it in tftp server directory.
    [root@voyager tftproot]# tftp
    tftp> get tp_recovery.bin

==> OK

  1. Connect PC with one of LAN ports, press the reset button, power up
    the router and keep button pressed for around 6-7 seconds, until
    device starts downloading the file.
  2. Router will download file from server, write it to flash and reboot.

Nothing happens. With tcpdump I see only:
11:10:08.293777 ARP, Request who-has tell, length 46
.. .............B..................
11:10:08.293817 ARP, Reply is-at 00:26:18:21:db:08, length 28
.. ....

No tftp traffic.

Note: it's an EU version.

Could you help me ?