iPad 2017 unable to restore/update I'm having issues restoring my daughter's iPad to working order, and I'm wondering what options I have.

She changed her passcode on it and then forgot it, so now it's permanently disabled. I'm resigned to having to wipe it (well I don't really give a shit about what she has on there anymore), but having issues getting it to a "blank slate".

It doesn't seem to be connecting to my Wi-Fi, so an over-the-air wipe from her iCloud account doesn't work.

I've tried putting it in recovery mode by holding the power and home buttons while connected to iTunes. This initiates the update process, however after downloading the 2.9 GB update, it seems to stop with a network error -3259 and then eventually the iPad just restarts back to disabled mode.

What other tricks can I try to get this back to a vanilla state so I can restore (an outdated) backup?

I'm trying this on a Windows 10 PC on an NBN 50 Mbps connection with the latest version of iTunes.
Download the restore image for your model of iPad from https://ipsw.me. You should be able to get the restore image for iOS 12.3.1 (current as of this writing).

Once you have the image, connect the iPad to your Windows PC, launch iTunes, and press and hold Shift key and click on the Update button. You'll be prompted to select a restore image. Point to the downloaded image. This should do away with the network error 3259 that you are getting.

Your iPad would be set up from blank state. You'll have an option to restore from an iCloud backup directly over-the-air.