Using a template inside a class
move the template method definiton to .h or define it in class. it is not a real function, only a prescription for functions. Like this:
class myTest
{
public:
    myTest();
    template &lt;class T1&gt;
    void funcOne(T1 arg);
};

template &lt;class T1&gt;
void myTest::funcOne(T1 arg)
{
        Serial.println(arg);
}

or this
class myTest
{
public:
    myTest();
    template &lt;class T1&gt;
    void funcOne(T1 arg)
    {
            Serial.println(arg);
    }
};