My power strip crackles when switched on. Can I still safely charge my phone there?

Contacts, whether when plugging a plug or when switching a switch, slowly approach the counterpart.
This creates an electric arc, because air can conduct electricity. You’ve often experienced that with a thunderstorm. The voltage in a socket or a switch is not so high that such a flash is to be heard within a kilometre distance, in your socket bar this is just a cracker.

If you switch high loads (e.g. a heating oven), the contact can naturally also be hot, the plastic melts or burns. Therefore, the number of consumers is limited to such a socket strip and, above all, the overall line. Your charger is just a fly shoot.