https://www.theguardian.com/world/2018/sep/07/kurds-renew-their-claim-for-idlib-as-final-battle-draws-near

Aggrieved Kurdish fighters quietly join Syrian regime side in battle for Idlib

If the U.S. backed Kurds are fighting with Assad. that's a huge problem for Turkey. However there is not much mention of this.

Russia Shares Syria War Experience With China in Largest Military Drills

https://www.newsweek.com/russia-china-power-military-drills-war-games-us-syria-assad-iran-1120080