The inexpensive D7DDC design ATU-100 100 watt autuners advertized on Ebay and Amazon work great.
$73 fully assembled: https://www.ebay.com/itm/134226040446
$30 kit, no enclosure: https://www.ebay.com/itm/154835157861
These can be modified to connect to the 4 pin Icom TUNER port. Operate from your transceiver TUNER button:
Solder a 560 ohm resistor to via "A6" on tuner. Connect to Icom TUNER pin 1 (_KEY).
Solder a 560 ohm resistor to "B" header on tuner. Connect to Icom TUNER pin 2 (_START).
Connect "+" header pin on tuner to Icom TUNER pin 3 (+12v).
Connect "-" header pin on tuner to Icom TUNER pin 4 (GND).
The current limiting resistors protect the tuner micro I/O pins from an accidental connection to +12 volts or ground.
Recommend strapping 100pF capacitors to ground on these pins to keep out stray RF.
Wnen the Icom transceiver senses 2 volts or more on _KEY when _START goes low, the Icom transceiver automatically limits power to 10 watts while tuning (when _KEY is then driven low by the tuner). On other transceivers, the operator mustmanually limit power to 10 watts while tuning, to protect the tuner's relay contacts.
Description of the _START and _KEY signals on the Icom and LDG antenna tuners: https://hamoperator.com/HF/AH-4_Design_and_Operation.pdf
Description of the TUNER connector circuit on the IC-7000: https://www.eham.net/article/18466
N7DDC ATU-100 Technical Description: https://github.com/Dfinitski/N7DDC-ATU-100-mini-and-extended-boards/blob/master/ATU_100_EXT_board/ATU-100_Extended_Board_User_Manual_eng.pdf