I will think Bitcoin to be the same as gold chain, it has a value in fiat but not yet converted to fiat. Hence I feel there is no need to declare.
I'm pretty sure customs would disagree with your reasoning. It can easily be used to buy illegal weapons or fund terrorism.
Of course, you could just as well reset the hardware wallet and just remember the recovery words. You can do that without hardware wallet too, 12 words in your mind is enough to carry millions of dollars now.
If I was planning on accessing some while there I'd put a seed in a dark corner of an SD card somewhere and restore a phone wallet.
There's another reason why I wouldn't bring a hardware wallet: it shows you own enough funds to buy a hardware wallet, so you're a good target to get robbed (I don't have one, don't rob me
). A good old "your money or your life", and you'll most likely hand over your PIN.
As far as I know this rule only applies if you carry cash in such amount or more then you have the obligation to declare, not credit cards or any other goods.
Credit cards are okay, because authorities can trace them. Bitcoin is a lot more like cash, it can't be traced, so customs will be very interested.
Though i haven't used any of the hardware wallets before, one stand the risk of losing their bitcoins once it gets missing.
That's why you have a recovery seed phrase.