I want to install OpenWRT on Linksys EA6300 V1.

I downloaded the file mentioned at "Firmware OpenWrt Install URL" on the page "Techdata: Linksys EA6300 v1", followed the steps mentioned in the page "Installing OpenWrt" and uploaded it via the upgrade firmware option from stock firmware GUI. The router reboots but returns in stock again, but to a lower version. Tried it again but same result. Doing a hard reset (30-30-30) or factory reset before and after install also does not solve the issue

Also tried it using the the actions described at "Installing OpenWrt via TFTP" but same result.

What am I doing wrong?

Can it be related to the fact that the uploaded file is a trx-file and not a bin-file, since the page "OpenWrt image conversion" mentions dat trx-files are used for upgrading openWrt only? But cannot find a bin-file for this router.

All all highly appreciated!