Lent money on an app, accounts have gone into collections

During the 2019 year, I lent money to strangers on an app. Some of which I had made a positive return of almost $500, in which case an additional $1000 to individuals have gone into collections. I'm currently at about -$500, and I was told that they do not issue a 1099 unless you make over $600. What can I do to claim that -$500 loss on my tax returns?