How were Arabs treated under Ottoman rule?
The Arabs had once ruled over much of the areas/territores of the Ottoman/Turkish empire; they had 'founded' Islam as a dynamic force in the first place, initially under the 'Rightly Guided' Caliphs (i.e. the Apostles of Muhammad) and then under the Ummayad and Abbasid empires.
However, by the 14th-15th centuries AD, the Arabs were in decline in the Middle and Near East and the Ottoman/Utmanli Turks, co-religionists but of a diferent ethnic and tribal composition, gardually began to take over the lands once controlled by the Arabs and also ended up eventually with their Sultans as 'Caliphs' of Islam.
Naturally, the Ottomans did not trust the Arabs who had once ruled/controled their dominions and still resented their downfall; and of all their subject nations, probably the Arabs suffered the most under Ottoman rule. They were given very limited role in power sharing and official/government positions and stern Turkish governors and large Turkish garrisons of troops were stationed in Arab areas. Their leaders and chiefs were humiliated and they were made to accept Turkish/Ottoman ways and subjugated to many sufferings.
Ultimately, during World War 1, the Arabs revolted against Turkish/Ottoman rule quite openly and with British/Allied help, helped defeat turkey and her German partner in the Middle East. Very famously, the story of the initial outbreak of the 'Arab Revolt' , to the time the Arabs entered Damascus under Prince Faisal of Hedjaz, in triumph, is told by TE Lawrence (''Lawrence of Arabia'') in his fine book ''The Seven Pillars of Wisdom''.