Installing LEDE on a Tenda AC9

@adonaros
It's a shame that 5Ghz on AC9 doesn't work as it defeats the similar price-ranged routers by a huge margin (source: https://www.digitalcitizen.life/review-tenda-ac9-ac1200?page=1). It was the reason I picked it up the first place.
The UI really is terible lol- I thought that the review was over-exaggerating things

I do not need wifi at all, and this device seems perfect for me. I made a custom firmware with the imagebuilder and now I can not get the rotuer into CFE mode to load the firmware. I set my eth0 to 192.168.1.2 mask 255.255.255.0 and i pinged 192.168.1.1 while holding the reset button in and plugging in the power cable. After 4 ping replies it goes away every time. Any suggestions?

ping: sendmsg: Network is unreachable
64 bytes from 192.168.1.1: icmp_seq=70 ttl=100 time=2484 ms
64 bytes from 192.168.1.1: icmp_seq=71 ttl=100 time=1460 ms
64 bytes from 192.168.1.1: icmp_seq=73 ttl=100 time=0.388 ms
64 bytes from 192.168.1.1: icmp_seq=74 ttl=100 time=0.413 ms
From 192.168.1.2 icmp_seq=107 Destination Host Unreachable

Try 192.168.0.1.

How did you solve / got around the "disappearing act" of the mini CPE web server?...

I didnt. I switched to a tplink archer c7 v5 before i saw the above suggestion. I will try 192.168.0.1 some time after i finish flashing 25 archers

I do have a Tenda AC9 V1.0.
I pressed reset for about 20 secs while powering up and the cfe mini browser appeared.
But both uploaded firmware files (openwrt-19.07.0-bcm53xx-tenda-ac9-squashfs.trx and openwrt-bcm53xx-generic-tenda-ac9-squashfs.trx) doesnt´t seem to work.
When the router boots up, he is available for about 3 secs at 192.168.1.1, but then the connection will be lost.
When i upload the original firmware all is well....
Any solutions?

By magic ?
You are very lucky, because I did this several times, and the CFE mini web server did never appear.

Can you please describe the proccess in details to access to it ?

That would be great.
Cheers.