Lake County) has known I’m a Y fan. I always had Y flags, banners and other paraphernalia in my office (or cubical in the early part of my career). I would guess the average was 50/50 Y fans vs. Utah fans among coworkers over those years. Sometimes more Utah fans, sometimes more Y fans, but never heavily leaning either team.
I can think of 1 coworker that ever tried to make it awkward. That ended quickly when I stuck to friendly rivalry banter. Haven’t worked with that coworker for over 5 1/2 years, but still text regularly, including discussing the rivalry, life and other sports. Always friendly, even when we discuss the rivalry.
About the awkward start... as mentioned above, I put up a flag in my office and other Ycentric paraphernalia first day on the job. This was an office not far from downtown SLC. A Ute leaning group, but the owner/ president/ CEO was a Y fan. The coworker worked in a cube that he basically had a direct view of my large Y flag as he walked away from his cubical. He stopped by my office soon after I put up the flag to say he was filing a harassment/ hostile work environment complaint and pointed to the flag. I worked to make sure the relationship was good, including when talking about Utah and BYU. I was soon fun to discuss the rivalry.