@Hubaiz
Thank you for the file ddserver_0.2-14_mips_24kc.ipk . I had some memory problems but found a way to get the system running.
Install and update Firmware:
https://openwrt.org/toh/tp-link/tl-mr11u
connect mr11u with a lan cable
Browser: 192.168.1.1
Internet connection is needed ->
Network/wireless add a new wirelessconnection and deactivate the existing one in the rooter.
Go to system/Software update list
install available Packages: uclibcxx
Start Terminal:
go to ddserver_0.2-14_mips_24kc.ipk folder (cd downloads)
scp ddserver_0.2-14_mips_24kc.ipk root@192.168.1.1:/tmp
ssh root@192.168.1.1
opkg install /tmp/ddserver_0.2-14_mips_24kc.ipk
if no errors its done.
Switch back the WLan configuration.
Change the password of the MR11U.