After following this topic and seeing some answers, I have come to the following conclusion:
If you want to cross a country's border and are afraid that customs will take your piece of paper, use:
Encryption: encrypt the mnemonic phrase using AES, GPG, use a hidden drive encrypted with veracrypt, transport the encrypted file on a pen drive, transfer it to the cloud (it's highly unlikely that you will access, for example, your Google Drive, OneDrive, etc. account). Make sure to use a strong password, but you will have another job to do, which is to remember this password or write it down offline in a safe place. But the advantage is that a password will not attract as much attention as a sequence of 12/24 words.
Seed division using shamir backup (slip-39) is something that I would not recommend at this time, despite the advantages offered, I've not yet tested this feature, in addition to having more work to store and carry a bunch of recovery papers of 3-5 for example, it would not be useful when traveling internationally.
Another strategy would be to keep copies of the mnemonic phrase (encrypted or not) with a relative or friend in the destination country. In this case, it's essential to add a BIP-39 Passphrase so that you don't run the risk of having it stored by the custodian for the time being. Using a passphrase has already been discussed extensively here, so it would be the most obvious solution and I'll not go into much detail about it.
Back on topic about hiding private keys. I remembered how I kept some notes hidden when I was little. I disassembled pen and made little scroll out of pittle piece of paper. Then I would put it in pen's tube and assembled pen back together. If the pen has opaque tube it will be pretty hard to discover the note.
I found this strategy very interesting, but don't doubt too much about the possibility of being discovered if you are (very, very) unlucky enough to have a customs guard on a bad day and want to search all your things.
I still think the strategy of using
seed-otp for encryption is the best of all, because in addition to creating plausible deniability even if they discover that you carry a seed with you, it is a totally random seed of your original seed that can only return to the original state using the source otp key, you can still use steganography to hide this phrase.