New to mikrotik routers having only just recently acquired a pre-owned hap ac2.

Attempted to netinstall the latest version of routeros (7.12) using debian 12 using the -r option, as I wanted to ensure that I was starting afresh with its configuration. However, that appeared to fail as it hung with what I assume was some sort of error - sendFile.

Subsequently attempted to install 6.49.10. This appears to have been successful, in that the process gets to 'Sent reboot command' then exits. However, it appears the unit is now stuck in etherboot. Whenever I power the unit on I am unable to make any connection to it using winbox.exe (running under wine), no details of the router appears in 'neighbors' no matter which ethernet interface I plug into. Wireshark shows no activity on ether2-5, whereas on ether1 the only packets captured are bootp. Furthermore if I make further attempts to run netinstall-cli, it finds the router straight away without having to hold the reset button down. This suggests to me, as I've mentioned previously that the unit is stuck in etherboot.

Any suggestions on how to recover the unit?

Likely a firewall issue, documented here for EL9.

If not, scan through the doc for other ideas. Wrong port, etc.

This I don't believe is a firewall issue. When running netinstall-cli it completes without error. It does not get stuck at any stage, sends the reboot command after sending routeros package etc and exits. When I run a packet capture with wireshark following reboot ether1 is spewing out bootp packets and there's nothing on the other interfaces. Also winbox running under wine can't find the router now matter which interface I use.

From this I simply conclude that the unit is stuck in etherboot. Even rebooting without holding down the reset button, and running netinstall-cli, the unit is found and recommences the install all over again, which, according to the documentation, should only happen if the reset button is held down (either before restoring power or immediately afterwards)

Any further ideas on how to move forwards?

arm images required not arm64.

I now have the unit up and running on 6.49.10

Since it's new device for you (and I'm guessing that your family's happiness doesn't depend on it yet), I suggest you to bite the bullet and (net)install 7.13rc on it. This version (finally) allows running modern wireless driver, which really unleashes full potential of this little gem.

Absolutely update routerboot (system -> routerboard -> upgrade) before trying to install ROS v7, too old routerboot can fail to boot newer versions of ROS.

Since it's new device for you (and I'm guessing that your family's happiness doesn't depend on it yet), I suggest you to bite the bullet and (net)install 7.13rc on it. This version (finally) allows running modern wireless driver, which really unleashes full potential of this little gem.

Absolutely update routerboot (system -> routerboard -> upgrade) before trying to install ROS v7, too old routerboot can fail to boot newer versions of ROS.

As I now have two of these (the second of which helped me discover the original error of my ways) I'll get the one I have working with 6.49.10 set up in the way that I want, and this will give me the freedom to test the cutting edge with the other.