Yes, this is a strange way to ask a question , but here it goes.
I recently upgraded from DSL to FIOS internet and my Linux Mint worked "out of the box" using the cable connection. Having read some of the horror stories in the past, I was wondering why it worked for me.
It's all a matter of user knowledge and equipment used.
If you have a user on DSL who is using a modem that is connected to a PC via USB it won't work with Linux since there are no USB drivers provider for Linux. However if the DSL hardware is a modern+router then the Linux PC is connected to an Ethernet port on the modern+router and it will work. Put an Ethernet switch on the modern+router LAN port and you can connect multiple different OS based computers or appliances.
Verizon just wants to support Windows. They have a hard enough time to just support that. Add more OS flavours in the mix and you logarithmically compound Verizon's support requirements.
As long as an OS or an appliance is TCP/IP compliant it will work with any ISP provided service. Granted the end user is kn owledgable enough to know the nuances of implementation. In some instyances it is a plug and play situation, in others not so much and needs user intervention.
In short, linux is TCP/IP compliant and it can work with DSL, FiOS, DUN or even Verizon Cellular Broadband.