data such as host name,
Okay why do they need to know that? Why do they need to know if the computer is called "Melissa's Laptop" or "Workstation 15, Internal security division"? Seems like this kind of data could if stolen be misused and it has minimal legitimate purpose IMO as anyone can put anything as host name and while in organizations it often corresponds to use it doesn't have to for individuals. Someone could call their machine "Mack's Porn Rig" and they only use it for doing banking and a little coding.
kernel version, desktop component versions, detailed information about hardware and drivers involved, screen size and resolution information,
This all seems legitimate enough, this would be helpful for understanding the hardware their users run on and targeting features or bug fixes.
network device MAC addresses,
Not great but there is an argument for it, they could just grab and send the first 3-4 octets which would give them the info they need on manufacturers without getting uniquely identifiable data that along with some of this other stuff is concerning for fingerprinting.
disk serial numbers,
Okay, what the fuck. Why do they need disk serial numbers? What possible use is there for that. Those are used for warranty claims and could be used as part of uniquely fingerprinting a computer and person. Not cool.
disk partition data,
This is vague enough. I guess one could choose to see this as just info about partitions in use say if there's also an NTFS partition that looks like a Windows install that would be useful but on the other hand data encompassed within a partition could also nefariously be read as allowing them access to all your data. Partition layout, partition labels, and file systems used on disks available to the system would be a clearer way to put this and erase any doubt.
information about the number of running processes and installed packages, versions of basic packages such as systemd, gcc, bash and PipeWire.
All this is also fine just technical data stuff.
For NAS getting something used from someone upgrading to something bigger on eBay is often a good route. Just be absolutely sure the model being sold meets your needs. Do you plan to run software on it for instance? Check what it can comfortably run first.
For drives. Server part deals always has good prices. I’d recommend only buying the ones with 1-3 year seller or manufacturer warranty though which is most of them. Easily half the price per TB you find most places. $150 gets you 14TB there.