Edit: Apparently in the US, any capital loss due to loss or theft is not considered taxable capital loss, so I guess I'm just SOL.
I'm glad I had diversified and my Celsius losses were only 25% of my crypto (of which, at the time, was only 3% of my total investments overall). I've completely exited crypto since this debacle and sticking with boring VTSAX and VTIAX entirely.