SG, is it normal not to receive any 4* ascension material from titan loot since 27.07.2020? Is it normal the elemental chests to appear 15-18 days period and the loot from them not to include any 4* ascension material?
Yes… 
Hitting higher level titans though, gives you more opportunity at better loot such as 4*AMs. Check out Show me your rewards to see what’s possible.
From 8* to 13* titans no 4* AM. Under 8* there is no sense to comment. 3 people killed rear 6* and no 4* AM or bonus.
Chests, titan loots and other stuff gives chances for 4* ascention mats, you never know what and when you will get 
Even mystic vision gives them.
I’ve got after few days on both accounts. No 4* mats but pretty often as for an elemental chest