A 70-year-old man with a 40-pack-year smoking history presents with chronic cough and exertional dyspnoea. Post-bronchodilator spirometry shows FEV1/FVC 0.58 and FEV1 55% predicted. He uses salbutamol as needed. According to the 2023 Canadian Thoracic Society COPD pharmacotherapy guideline, what is the most appropriate initial maintenance pharmacological therapy?