You can pick the file by Intent.ACTION_OPEN_DOCUMENT and then you have permission to read it.

import android.content.Intent;
import android.net.Uri;
import android.os.Bundle;
import android.util.Log;
import android.widget.Button;
import androidx.activity.EdgeToEdge;
import androidx.activity.result.ActivityResultLauncher;
import androidx.activity.result.contract.ActivityResultContracts;
import androidx.appcompat.app.AppCompatActivity;
import androidx.core.graphics.Insets;
import androidx.core.view.ViewCompat;
import androidx.core.view.WindowInsetsCompat;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class MainActivity extends AppCompatActivity {

    Button selectFileButton;
    ActivityResultLauncher<Intent> resultLauncher;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        EdgeToEdge.enable(this);
        setContentView(R.layout.activity_main);
        ViewCompat.setOnApplyWindowInsetsListener(findViewById(R.id.main), (v, insets) -> {
            Insets systemBars = insets.getInsets(WindowInsetsCompat.Type.systemBars());
            v.setPadding(systemBars.left, systemBars.top, systemBars.right, systemBars.bottom);
            return insets;
        });
        selectFileButton = findViewById(R.id.selectFileButton);
        selectFileButton.setOnClickListener(view -> {
            ChooseFile(resultLauncher);
        });
        resultLauncher = registerForActivityResult(
                new ActivityResultContracts.StartActivityForResult(),
                result -> {
                    Log.i("TAG", "resultLauncher: " + result.getData().getData());
                    String text = openTextFile(result.getData().getData());
                    Log.i("TAG", "resultLauncher: " + text);
                    
                    // process the text . . .
                }
        );
    }
    public static void ChooseFile(ActivityResultLauncher<Intent> resultLauncher) {
        Intent intent = new Intent(Intent.ACTION_OPEN_DOCUMENT);
        intent.addCategory(Intent.CATEGORY_OPENABLE);
        intent.setType("text/plain");
        resultLauncher.launch(intent);
    }

    public String openTextFile(Uri uri) {
        try (InputStream inputStream = getContentResolver().openInputStream(uri);
             InputStreamReader inputStreamReader = new InputStreamReader(inputStream);
             BufferedReader bufferedReader = new BufferedReader(inputStreamReader)) {

            StringBuilder stringBuilder = new StringBuilder();
            String line;
            while ((line = bufferedReader.readLine()) != null) {
                stringBuilder.append(line).append('\n');
            }

            String fileContent = stringBuilder.toString();
            return fileContent;
        } catch (IOException e) {
            e.printStackTrace(); // Consider better error handling
            return null;
        }
    }
}