Does your isp support 3rd party modems?

I would assume so if you are asking.

Are you fine with having 2 devices in the area where this dsl modem needs to be?

so does your ISP router have a built in modem? Because most consumer routers are just Ethernet, and you would need a separate modem to convert from DSL to Ethernet for the router to be able to handle it. I personally have no experience with DSL so I can't offer any advice on what to get.

it's important to know the differences between a modem, a router, and a switch as many device have multiple in one

A modem convers an analog signal like a telephone line in dsl's case to a digital medium like Ethernet

a router acts as a manager for a subnetwork (your lan) to bridge and firewall to the rest of the internet

A switch allows multiple devices to communicate with each other

If you have a combo box you'll have a harder time. There's very few available for that. Need to find out what modem is needed and set that up. Then use any router you want. Or find out which 3rd party combo boxes are compatible