The mnemonic seed WeTheNorth issues at registration is the recovery path for your account. Anyone with the mnemonic owns the account. Where you store it matters.
Paper
The default. Write the mnemonic in your own handwriting on a piece of paper. Store in a physical location only you access. Multiple copies in different physical locations you control is fine.
Metal
For long-term cold storage, engrave or stamp the mnemonic into a metal card. Not paranoid, just future-proof. Fires happen.
Encrypted local file
File encrypted with a passphrase only you know, on encrypted local disk that never syncs to any cloud. GnuPG can encrypt a file with a passphrase in one command.
KeePassXC
Password manager database on encrypted local storage. Not a cloud-synced password manager.
Do not
Screenshot the mnemonic. Save it to iCloud, Google Drive, Dropbox. Store it in a browser autofill. Email it to yourself. Take a photo. Any of these moves the mnemonic out of your exclusive control.