This app was mentioned in 20 comments, with an average of 1.20 upvotes
monkey bloon series, last 2 are free (with IAP ofc)
The newest would be Bloons TD Battles
Although I just linked to desktop steam download... I'm doubting that'll work on mobile.
There's also Bloons TD Battles, which the same as 5, but it is online splitscreen multiplayer, I've played for a while & was pretty fun.
Have you tried Bloons TD Battles?
https://play.google.com/store/apps/details?id=com.ninjakiwi.bloonstdbattles&hl=en
BTD: Battles and Monkey City are both free!
https://play.google.com/store/apps/details?id=com.ninjakiwi.bloonstdbattles
https://play.google.com/store/apps/details?id=com.ninjakiwi.monkeycity
(Also available on iOS, if you need it :) )