The one exception I've found so far is that the UNVR-4 system software in older models is stored on a very cheap USB flash drive, and I believe they write logs to it too. Mine failed a few months before warranty expired so I just replaced it with an SSD and SATA->USB 3 adapter I had laying around. Works great, is snappy, and should hopefully last quite a bit longer.
A fairly cheap NAS from them for local storage, and then basically any ip camera you can find will mostly just work. (NAS I'm using: https://www.amazon.com/Synology-Bay-DiskStation-DS220-Diskle...)
They offer surveillance station (https://www.synology.com/en-us/surveillance) as a free app for most of their models.
My entire setup (3 cameras, NAS, hdds, POE switch) cost me under $1000, and I get pretty much every feature that most of these cloud camera services offer.
- Remote viewing on my phone (https://play.google.com/store/apps/details?id=com.synology.D...)
- Activity alerts and optional triggers for recording
- Viewing through any browser
- Multiple user accounts
Plus if I want it, Surveillance station has a whole host of other features that I currently don't need, but are nice to have (ex: automated cloud backups, offsite storage, CMS, Action rules, etc)
As a nice little bonus - I pay zero in monthly costs for this outside of the power to run the cameras & NAS
My initial setup cost ran slightly higher than something like Nest or Google Home (ex: I paid 1k vs the roughly 400 it would have cost to buy the cameras from a cloud service) but 4 years in I'm now in the positive on the investment, since I don't have a recurring 14/month subscription charge.
So long story short - It's still my data, it's costing me less over time, and I get feature parity.
The downside is it requires a little more configuration and setup.
My biggest gripe right now is when you get a notification and tap it on Android, you get such a cut down UI, it doesn't even have a scrubber and you can't fast forward or rewind. Just a completely barebones player you can't control. Once you exit that and go to the camera history, you get a normal player with controls. Makes no sense to me whatsoever.
Anything the integrates with homekit secure video will be e2e encrypted