local cloud storage solution I have got a 1 terabyte external hard drive, and I would like to find a seamless way for my android device (an HTC one mini) to be able to access that hard drive.

In the old days when I wanted to do "cloud", I would plug such a device into my always-on-always-connected-to-the-internet linux and just share the device -- let other machines mount it. Of course this still works fine -- but I don't know how to do this via Android, or via Windows.

Nowadays we have cloud solutions like Dropbox, which works great on my Android device, but I have limited storage space (unless I pay -- but I already paid for the external hard drive).

Ideally I am looking for something with the simplicity of Dropbox but with everything under my control. I considered git for a while, and there are ways to get an android device to run git, but you seem to only have a limited end-user experience, and you seem to have to actually upload projects rather than being able to access them from afar -- and my android device doesn't have that much memory.

I tried sparkleshare, but I can't find a client for Android.

I tried every option that ES File Explorer offers, but they all seemed to involve losing control of the cloud storage.

Is it possible to do this via LAN somehow? The problem is that my Android device will typically be moving from wireless network to wireless network and will not always be on the same network as the external drive.

Basically I think I am asking for a way to plug a terabyte hard drive into my phone in a wireless way. This problem has surely been thought about seriously!
Did you take a look at OwnCloud and similar solutions? Not (yet?) as comfortable as dropbox, but open source, runs on Linux (so you can stick with your Linux-mount solution), and it has an Android app. For a quick overview, you might want to first take a look at this Wikipedia article. If that sounds interesting, next source to investigate might be e.g. How to Set Up Your Own Private Cloud Storage Service in Five Minutes with OwnCloud :)