Dart libserial is unable to open `/dev/pts` devices - dart

Question

I am monitoring a serial device via a jpevulator:
jpnevulator --read --ascii --tty /dev/ttyACM0 --pty --pass --read --ascii --timing-print
jpnevulator: slave pts device is /dev/pts/3.
jpnevulator: Use --read or --write, but not both. Performing a read this time.
**strong text**
And I made a simple programm that sends a string and reads from the serial port as well:
import 'package:libserialport/libserialport.dart';
import 'dart:typed_data';
void main(List<String> arguments) {
final port = SerialPort("/dev/pts/3");
if (!port.openReadWrite()) {
print(SerialPort.lastError);
}
port.write(Uint8List.fromList("Lorem Ipsum".codeUnits));
final reader = SerialPortReader(port);
reader.stream.listen((data) {
print('received: $data');
});
}
But I get the error once I dart run it:
Building package executable...
Built serial:serial.
Unhandled exception:
SerialPortError: No such file or directory, errno = 2
#0 Util.call (package:libserialport/src/util.dart:39:7)
#1 _SerialPortImpl._init (package:libserialport/src/port.dart:221:10)
#2 new _SerialPortImpl (package:libserialport/src/port.dart:211:42)
#3 new SerialPort (package:libserialport/src/port.dart:72:38)
#4 main (file:///mnt/data/Kwdikas/dart/serial/bin/serial.dart:5:16)
#5 _delayEntrypointInvocation.<anonymous closure> (dart:isolate-patch/isolate_patch.dart:295:32)
#6 _RawReceivePortImpl._handleMessage (dart:isolate-patch/isolate_patch.dart:192:12)
Any idea why? I am running it on linux mint. I am using flutter installed dart that is shipped as snap:
$ whereis dart
dart: /usr/bin/dart /usr/lib/dart /snap/bin/dart
And I have installed it using classic confinement:
sudo snap install flutter --classic