I've been thinking about this recently and have a few tentative conclusions.
- My government (.au) runs almost entirely on the MS cloud/productivity stack, as do most large businesses. This is the stuff that's going to get resources when there are outages, conflicts, or difficult decisions have to be made. Assuming a degradation over the next decade or two, you could do worse than align your business or personal computing with PCs and MS tech/services - by the time you're facing major outages there are probably bigger problems outside your window. Even in extended collapse downturns there will be some work available to keep this stuff ticking along for many years.
- Intermittent connectivity is to be expected, but also the risk of suddenly losing access to some resource permanently, be that dependencies, documentation, software downloads, or your cloud data. At a minimum all cloud data you care about should have a full offline copy on local disk in a format that is usable. (This seems generally true of both Apple and MS cloud services, if you have a fully synced Mac or Windows PC with the right settings.)
- Development environments with batteries-included standard libraries will offer the most bang-for-buck, which can be installed from offline installers. Being able to build custom GUI apps on demand for whatever hardware your customer has is very helpful. I think .NET MAUI is very interesting here, especially if they end up gaining Linux GUI support. Linux is a great way to bring old laptops into service.
- When advanced technology manufacturing becomes too resource intensive and expensive for many people to buy, larger computers etc. will give way to phones, often crummy ones. Expect lots of Androids and hand-me-downs.
- There will be good trade in second-hand hard drives and batteries that are not too worn. If you can bodge together USB powerpacks from scavenged batteries then certain kinds of USB-powered devices should be able to run for decades. Ultimately I expect old Android devices to be dominant platform because they are numerous, relatively inexpensive, hackable and portable.
- If your value derives from what you have (hardware, stashes of offline data etc.) then expect it to be taken from you. Skills are more helpful - so long as they are actually useful in the computing environment of the time.