My bank keeps freezing the card the first time I pay in a new country Logistics

The setup that survives is redundancy, not better notices. Notices are ignored by most fraud engines anyway.

What I carry: two accounts at two institutions in two different countries, on two different card networks, and one of them is a fintech account that expects international use and does not care where you are. Never keep both cards in the same bag.

Three things that have saved me repeatedly. Write the bank fraud line international number, the one that works from abroad, on a physical card in your wallet, because you cannot get it from a website you cannot log into. Keep a hundred in cash of a widely accepted currency somewhere that is not your wallet. And make your first transaction in a new country a small withdrawal at a bank ATM during business hours, so if it does trigger a block you are standing next to people who can help and you are not stranded at a train station at midnight.

Worth looking at what your first transaction actually is, because there is often a pattern. Unattended terminals are the classic trigger: fuel pumps, toll gates, ticket machines, because they send an authorisation with an odd amount and no cardholder present verification. Airport transport is usually one of those, which is why it fires on day one every time. Do a supermarket or a bank ATM first and the same card sails through for the rest of the trip.

One more failure mode to design out. If your bank sends one time codes by SMS to your home number, and your home SIM is at the bottom of a bag with no service, you cannot authorise anything even when the card works. Keep the home number alive on an eSIM or a cheap dual SIM handset, and move to an app based authenticator where the bank supports it. I lost a day to exactly this.

Screenshots of your cards, front and back, stored somewhere you can reach without your phone. Sounds paranoid until a bag walks off and you cannot even tell the bank which card to cancel.