@atthis_pictus
First answer: adding on to what others have commented about fandoms in general that has good ace representation, The Magnus Archives podcast main character is ace and bi and in a relationship by season 5. The fanworks and shipping in that fandom are excellent.
Second answer: Kaeya Alberich who is fun and flirty and likes to hang out in bars, gets a reputation of being a slut, but he's ace and it's all part of how he investigates criminal rumors.