The lighter port is a 12V high current source. I speculate that it is difficult to break. To use it to charge a phone, there must be a 12V to 5V adapter (USB style??). The charging adapter is defective. Replace the adapter.
If the lighter port also has an associated USB charging port, then the mechanic blew that out as well.
This sounds more like a failure of the alternator/voltage regulator system in your Jeep, causing voltage spikes above the acceptable ~12V to ~14V range. You can test this with a voltmeter that has a peak hold function, or an oscilloscope as @jsotola suggests.
"The mechanic let the battery die" sets off alarm bells for me. Did the car sit unused for weeks? Was there already a defect in the alternator/charging system? Are there corroded or intermittent connections in the electrical system? Stop plugging in phones and get a competent automotive electrical technician to investigate.
It sounds like the effects of a load dump or a reverse battery jump. Disconnecting a cable from a weak or bad battery while is charging by the alternator will generate a massive load dump. I would expect the battery when Fully charged to measure about 12.6 volts maybe a bit more, if less then this it is not charging. When the engine is running, this measurement should be 13.7 to about 15 volts. I have seen higher, this is not an absolute value but an approximation as each system is different. Many of the Jeep vehicles do not have a regulator per say. They PWM the alternator with either the body computer or engine computer depending on year and model. I believe you may find more damage over then next few months. Automotive electrical systems are very nasty.