After figuring out, that i have one with a Hynix Flash, i downloaded openwrt-19.07.2-lantiq-xrx200-avm_fritz3370-rev2-hynix-squashfs-eva-filesystem/kernel.bin from here: http://downloads.openwrt.org/releases/19.07.2/targets/lantiq/xrx200/
Although the related device page is saying that 18.06.8 is the current release i think that's the right one, because in the release folder of 18.06.8 there is only a sysupgrade file.
But then in the installation routine (with LAN cable) i stumbled across some things, i'm not really sure how to deal with. I resetted to factory settings before.
I wasn't able to connect to the device within 5 seconds after powering up. I had to wait longer, but the box doesn't seem to reset after 30 seconds, so i ignored this one.
When issuing the first command (quote USER adam2) in ftp the response is "230 User @SkipAuthFromHomenetwork logged in." Consequently the command "quote PASS adam2" also failed: "503 Login with USER first." I decided to keep this in mind, but go further. At least it seems that i'm already authenticated, so not that bad.
When issuing "quote SETENV linux_fs_start 0" the output is: "500 'SETENV linux_fs_start 0': command not understood." I don't know what this means. Should i proceed or is there something wrong in the sequence before?
But today i'm not able to access it for whatever reason. I'm quite sure, but i can't guarantee that i didn't make a mistake while configuring the device, it was late.
So today, i try to enable failsafe mode. I press the "WLAN" button during startup and the power led is flashing red and fast. Do you know if this is really the failsafe mode? The device should open up an ssh server listening on 192.168.1.1 when in failsafe mode, right?