Dude dsl is ancient and ISPs no longer maintain the lines… do you have other options? replace router? replace modem? replace lines to house?

Why don’t you invest in a really good router that has SQM. QoS on most routers is assssss.

Unifi SE. Saw night and day difference in my wired connection compared to my nighthawk.

Eero could work as well.

Use solid copper and legitimate ethernet cables

Monoprice cat6a OR fs.com

the modems they provide are trash and use the intel puma chipsets even to this day