Thanks a lot.
This is what worked for me (INSTEAD OF MY_PASDWORD NEED TO PLACE THE CORRECT PASSWORD AND REMOVE THE SPACE FROM THE HTTP ADDRESSES):
Turning off 5G:
SESSION_ID=$(curl -k -s -d '{"jsonrpc":"2.0","method":"call","params":["00000000000000000000000000000000","session","login",{"username":"root","password":"MY_PASSWORD"}]}' http:// 192.168.8.1:8080/ubus/ | grep -oE '[a-f0-9]{32}')
curl -k -s --data-raw "[
{\"jsonrpc\":\"2.0\",\"method\":\"call\",\"params\":[\"$SESSION_ID\",\"uci\",\"set\",{\"config\":\"wireless\",\"section\":\"mt798112\",\"values\":{\"disabled\":\"1\"}}]},
{\"jsonrpc\":\"2.0\",\"method\":\"call\",\"params\":[\"$SESSION_ID\",\"uci\",\"set\",{\"config\":\"wireless\",\"section\":\"wifi5g\",\"values\":{\"disabled\":\"1\"}}]},
{\"jsonrpc\":\"2.0\",\"method\":\"call\",\"params\":[\"$SESSION_ID\",\"uci\",\"apply\",{\"rollback\":false}]},
{\"jsonrpc\":\"2.0\",\"method\":\"call\",\"params\":[\"$SESSION_ID\",\"file\",\"exec\",{\"command\":\"/sbin/wifi\",\"params\":[\"down\",\"mt798112\"]}]}
]" http:// 192.168.8.1:8080/ubus/
Turning On 5G:
SESSION_ID=$(curl -k -s -d '{"jsonrpc":"2.0","method":"call","params":["00000000000000000000000000000000","session","login",{"username":"root","password":"MY_PASSWORD"}]}' http:// 192.168.8.1:8080/ubus/ | grep -oE '[a-f0-9]{32}')
curl -k -s --data-raw "[
{"jsonrpc":"2.0","method":"call","params":["$SESSION_ID","uci","set",{"config":"wireless","section":"mt798112","values":{"disabled":"0"}}]},
{"jsonrpc":"2.0","method":"call","params":["$SESSION_ID","uci","set",{"config":"wireless","section":"wifi5g","values":{"disabled":"0"}}]},
{"jsonrpc":"2.0","method":"call","params":["$SESSION_ID","uci","apply",{"rollback":false}]},
{"jsonrpc":"2.0","method":"call","params":["$SESSION_ID","file","exec",{"command":"/sbin/wifi","params":["up","mt798112"]}]}
]" http:// 192.168.8.1:8080/ubus/