There is/was a game. Can’t find it in AppStore right now, but it’s on my phone. Maybe it got deleted? You could Google for it.

Ancient Empires Reloaded

Strategy/Tactics
Completely free, no IAP and no ads. (!)

Campaign
Scenarios
Skirmish
Online Multiplayer + LAN
Map Editor (!) with the possibility to upload your maps so other can play them/download Maps which were created by other players

Extremely difficult
Lovely old school 2D graphics
iOS and Android

Pokemmo

Brawl stars, been playing for like 5 years

Yu-Gi-Oh Duel Links

Here are the mobile games I play almost daily:

Mech Arena: Robot Showdown (sweaty 5v5 death match and control point battles in mechs. Very niche. You like it or hate it)

Shadow Fight 3 (timing and reaction based combat. Mortal combat graphics but tekken-like moves, many weapon and armor sets to collect and playstyles to get used to)

Super Mecha Champions (fight on foot or in mechas... diverse playstyles in mechas. Download and go to training to try them out)

The Wolf Simulator (run around as a magic wolf timing animals and other wolves)

The Sandbox Evolution (create your own and play other pplz sidecrolling environments with many effects and physics)

Pokemon Unite (like LOL but with pokemon)

PAKO

Cookie Run Kingdom!! It is a nice little game that will keep you on it quite often to upgrade and brings in cookies from several games.

World of kings

Clash mini is in beta and testing depending were you live. So far it’s a pretty big game made by supercell so your clash of clans / clash Royale / brawl star guys.

Recommend looking up how to play Catan if you haven't already tries it (board game). Lots of potential depth and if you Google colonist.io you can play via browser for free. Other than that I'd say treat a free stock trading app as a game after putting in like 10$ or the new phone version of Diablo (although after buying d2r on ps4 I'm seriously chapped ass at blizzard for a while).