Privacy.com. You can mint a credit card with a $0 limit (or $1 if they need to do a test transaction) and kill it right after.
In Europe you can probably use Revolut, they let you generate single-use cards.
Please note however that websites can tell it's a single-use card and refuse to accept it. Most recently Amazon and their related services (Twitch etc.) started refusing them.
Yeah I already have Revolut but those single use cards can't be used on subscribtion services sadly.
There's KOHO for Canadians, still not a proper Privacy.com replacement but you get two Mastercard cards (one physical & one digital) and they are refillable via Interac payments.
When doing trials, I set a few dollars on the card to ensure if they try to do a 1$ transaction to verify the card and I'm good to go. Even if I forget to cancel, the payment won't pass.
Every damn time. IMO, it's not really free if it requires a payment method; free trials should automatically end when the time is up instead of making you the one responsible for canceling to avoid being charged.
