Calls to methods of external classes in lambda functions java

Originally I had a class with a lambda function in a java class.

        final Map<String, UserBean> users = persons.entrySet().stream()
            .filter(entry -> !entry.getValue().getIsActive().booleanValue())
            .collect(Collectors.toMap(
                entry -> entry.getKey()
                , entry -> entry.getValue()));

But sonar gave me a suggestion: Lambdas should be replaced with method references

So I started to output to external methods. I started by adding to the same class where the lambda was, a function that returned the key. And update the lambda as follows:

        final Map<String, UserBean> users = persons.entrySet().stream()
            .filter(entry -> !entry.getValue().getIsActive().booleanValue())
            .collect(Collectors.toMap(
                    this::<String>getEntryKey
                    , entry -> entry.getValue()));

This worked perfectly for me and the sonar suggestion was only marked on the arrow that was on the bottom line of the statement that I modified. The issue is that I realized that this warning was repeated in many places in the code. So I started to make a utility class so as not to repeat code.

The utility class I have has two methods to get the keys and values ​​of a map:

public class LambdaUtils {

private static final LambdaUtils INSTANCE = new LambdaUtils();

public static LambdaUtils getInstance() {
    return LambdaUtils.INSTANCE;
}

public <K> K getEntryKey(Entry<K, ?> entry) {
    return entry.getKey();
}

public <V> V getEntryValue(Entry<?, V> entry) {
    return entry.getValue();
}
}

The problem is that now I don't know how to add that call to the utility class methods inside the lambda.

    final Map<String, UserBean> users = persons.entrySet().stream()
            .filter(entry -> !entry.getValue().getIsActive().booleanValue())
            .collect(Collectors.toMap(
                    this::LambdaUtils.getInstance().getEntryKey() //ERROR
                    , entry -> entry.getValue()));

How can I make the call to that external method inside a lambda?