For what it's worth, the iPad feels great in terms of size and construction, it has a fantastic screen and the overall UX/UI is pleasant. Unfortunately, it's not usable as a short term laptop replacement and basic computer tasks are just not possible, especially not offline.
EDIT: of course that doesn't help with the loading of open source software on the device.
Not to say that the iPad Pro is a Windows tablet replacement, to me they’re still very much distinct products right now. iPad OS isn’t (yet?) a macOS replacement for developers and power users.
Loading software from outside the App Store is not going to happen, but they are, slowly but surely, expanding to support other tasks.
If that was non-negotiable why did you even consider an iPad Pro in the first place?