Put the TV on a system with an exercise bike so you have to bike to make the electricity to watch it. At least you'll get moving and that is also self limiting in how much you watch.
I can't really fathom not being interested in anything other than TV though!
For me the issue is I'm interested in way too many things, here's a sampling of things I do just from my current projects list
weaving, spinning, knitting, scrapbooks, photography, genealogy research, historical research, reading novels, writing novels, genetics research, naalbinding, sewing historical clothing, sewing modern clothing, leather working, target shooting, museum cataloging, weight lifting and yoga.
And if I include the things on my someday/maybe list you can add
learn calligraphy, learn how to bind books, learn to speak Welsh fluently, hike to the top of a fourteener, board member of several associations I care about, learn proper knife skills, learn more charceuterie (sp?), draw cartoons, learn needlepoint, learn simple woodworking, pen & ink drawing, learn to shoot skeet, clean my fossil collection for museum style display, write a screenplay, weaving clothing fabric then sewing the clothing, quilting, write an app for farm data collection for mobile computers, convert our old vinyl records to digital files, digitize historical photos, do more puzzles, build a solar oven, and so on.
There are thousands of fun and interesting things to do so start looking at something and find one that you can try instead of TV!
I'd make a point of trying to do one thing new each week or at least month until you find something that appeals to you to do more than one of.