Well, I think we are step further.
I was
git checkout v21.02.1
modifiied
tools/firmware-utils/src/tplink-safeloader.c
compile with default config (only changes target to only archer-c6-v2 )
and I was able to install openwrt via gui
root@OpenWrt:~# cat /proc/cpuinfo
system type : Qualcomm Atheros QCA956X ver 1 rev 0
machine : TP-Link Archer C6 v2 (EU/RU/JP)
processor : 0
cpu model : MIPS 74Kc V5.0
BogoMIPS : 385.02
wait instruction : yes
microsecond timers : yes
tlb_entries : 32
extra interrupt vector : yes
hardware watchpoint : yes, count: 4, address/irw mask: [0x0ffc, 0x0ffc, 0x0ffb, 0x0ffb]
isa : mips1 mips2 mips32r1 mips32r2
ASEs implemented : mips16 dsp dsp2
Options implemented : tlb 4kex 4k_cache prefetch mcheck ejtag llsc dc_aliases perf_cntr_intr_bit cdmm contextconfig perf
shadow register sets : 1
kscratch registers : 0
package : 0
core : 0
VCED exceptions : not available
VCEI exceptions : not available
I do not like this "C6" line but this is a little.
Now I wil test if everything works.
Thanks everyone for your efforts (and patience)