I run an agency and hire through upwork quite a bit, so I see the other side too. I think upwork already limits how many jobs people can apply to, but I still see tons of brand new accounts, so people clearly found ways around it.

One thing that really stood out to us during the hiring proccess on upwork is candidates who sent a short Loom with their face, walking through the challenge and how they'd solve it. Much easier to tell who actually understands the work. Might be worth trying from the freelancer side.