I don't think deniable encryption is needed, you just need to not say under oath "there is nothing on the drive that could incriminate me". If you say that you lose your protection and they can force you to provide the contents. Destroying keys, including wiping a LUKS header, wiping a TPM, destroying a USB hardware security key, etc. is destroying evidence and a crime. Not providing your really long password is not a crime, as long as there is some doubt (doubt you and your lawyer can carefully cultivate) regarding the fact that nothing on the drive incriminates you.

> Not providing your really long password is not a crime

What about not providing a PIN? How is that different from password? Proper PIN protected smartcards will lock you out after several wrong attempts and would require a PUK. And you might not remember that, genuinely. What then?

Intentionally entering wrong pins to lock out is probably destruction of evidence, and pins are so short I would not trust them. Just have an at least 15-length base32 password that's randomly generated with `echo "$(openssl rand -base64 20 | base64 --decode | base32 | head -c 15)"` or whatever. You might want it to be lowercase instead, or base64 for more entropy. That command should be secure on OpenSSL 1.1.1 or later, and combined with argon2id over 4GiB of memory and 12+ rounds, should be pretty much uncrackable.

You don't need to trust PINs, they aren't passwords in technical sense. And you don't need to enter wrong PINs either, if someone else tries they would reach a limit very soon.

It's all seems pretty arbitrary to me as to whether something is considered destruction of evidence and it's very US-centric anyway. So I'd say yes, deniable encryption is needed. If they decide you're not playing ball, then you'll be punished. The difference is whether they will use a legal system for that in a First World country or something else if you're not so lucky.