From what I've seen on Reddit, they solve the chicken-egg problem by having you buy some crypto (with fiat, below the threshhold amount), withdrawing it and then sending it back.
I can imagine that if you contact support they'll eventually offer another solution, but they could make you wait for weeks while your funds are stuck.
By solve I mean "solve",
Which means you've now gone from one deposit that doesn't stand out much on chain, to a very obvious pattern of receiving sats from the exchange and sending them back, all using the same address. Plus your bank sees a small transaction going to an exchange and a large one coming back, which might trigger their alarm and they hold you fiat ransom too.
And of course this fiat transaction pattern tells your bank that you're a self-custodial person.
