Not entirely sure but I believe this is due to something changed in Python 3:
File "/home/.../python-dali/dali/driver/tridonic.py", line 258, in send
sn = struct.unpack('B', data[1])[0]
TypeError: a bytes-like object is required, not 'int'
i.e. using subscription notation on struct.Struct seems to return the byte value as int
Not entirely sure but I believe this is due to something changed in Python 3:
i.e. using subscription notation on struct.Struct seems to return the byte value as int