Help Installing OpenWrt on OY-0001

I've looked online and the only project that seems to have up to date firmware for this relic is OpenWRT, I've read the wiki page and says the installation method is unknown. I've got a custom firmware installed already which came from the VPN service provider that it was used for. That service provider is long gone and I need better firmware to be able to use PPTP. The options that I have are:

And I've tried uploading and executing the upgrade, kernel and snapshot bins that are in the releases and wiki page but all i get is.

processing file openwrt-21.02.1-ramips-mt7620-ohyeah_oy-0001-squashfs-sysupgrade.bin
Decoding file
bad magic number gzip: invalid magic /tmp/upload/openwrt-21.02.1-ramips-mt7620-ohyeah_oy-0001-squashfs-sysupgrade.bin encryption=NO
gunzip test failed, now decryptinggunzip test returned gunzip -t /tmp/upload/upgrade/openwrt-21.02.1-ramips-mt7620-ohyeah_oy-0001-squashfs-sysupgrade.bin >/dev/null 2>&1;echo $?decompressing and extracting files
failed to extract upgrade file openwrt-21.02.1-ramips-mt7620-ohyeah_oy-0001-squashfs-sysupgrade.bin

Any help is appreciated.

There is no factory image and that means you need to hook up a serial console and load the firmware via tftp. Mediatek devices also have a recovery mode if powered on with reset button pressed. You can try that and listen with wireshark for requests