Here’s how to do it with every character in the support category.
Lucio: Boop her when she starts shooting, it will throw off her aim for the clip (most Tracer’s follow a pattern of blink, then shoot, so look to boop when she blinks). Aside from that you should win most duels because of your slippery hitbox and sustain.
Brig: Use armor pack. Congratulations the enemy Tracer is throwing. And if you somehow still have trouble then try whip shotting right when she starts shooting, you will likely hit her, proc inspire, and force her to recall/retreat.
Mercy: Using GA and superjump you should be able to get out of her effective range easily, and if she continues to chase you she will have to expend lots of resources to do so, and your teammates will have a much easier time killing her.
Moira: If she starts attacking you… fade away. Your effective range is longer than hers and if things get dicey just throw an orb.
Ana: A harder match-up to be sure, but if you use sleep dart when they start shooting you will force them to blink away giving you time to get help from your team. Never use bio nade against a Tracer that isn’t in your face, they will always dodge it. If you get the sleep on a Tracer, make sure to wait three seconds before waking her up, and use a primary fire to do it, then when she recalls to the same spot hit her with the primary/nade combo. Or better yet, grab literally anyone on your team and have them one-shot her.
Baptiste: If they have pulse bomb make sure not to use it, and if you are forced to, let your team know that there is a pulse bomb and you don’t have IF for it. Other than that regen boost and the threat of you one tapping her with three headshots should make her think twice before jumping you as long as your aim is good.
Zen: Lmao, who plays Zen? Anyways, don’t discord her because you aren’t likely to kill her without two headshots, so keeping it on the enemy Rein will get you much more value.