For desktop software which I use for work and personal things (like say Word) or what about infrastructure things like OpenDNS?
What about Comcast? Am I on a residential line or a commercial line?
So, in an office i can use my CCTV at home (private), but when I use CCTV at home to check my office, then it's business.
Chromecast used for display to present smthg to customers outside is clearly business, while watching Netflix while work ist private.
So the question is, do you use something for somehow earn money? Then business.
For mixed-used items if you can theoretically deduct at least part of it from your taxes as a business expense then you should consider it business, whether you deduct or not. https://www.irs.gov/publications/p535#en_US_2022_publink1000...
Since software licenses typically can't be paid for as mixed use, it seems you'd theoretically have to either buy both a home-use license for your personal use and a business license for your business use, or just make it easier and buy the single business license and use that for both business and personal use.
For things like internet or hardware that are marketed as business or residential you'd want to read the terms of service (TOS) to determine if these are just marketing terms, or TOS legal requirements.