Since Friday- on Android Mobile all Adventure, Dungeon, 7 floors Dooms, and 3 rounds of Delves, 3 rounds of explore, and 5 PvP - for a total of 3 gnomes.
That’s 92 battles = 3 Gnomes…
but my Account on STEAM on the (PC desktop) has 7 for 1/2 that work…
It’s not the first time I have seen the drop rate differ on Android verses PC.
Tower of Doom doesn’t have gnomes at all
Neither does Delves
So that drops your total to 35-40 eligible battles. So seeing 3 Gnomes in that amount, I would say is quite lucky.
In future it is best to focus on low level explore to maximise Gnomes if you are after something in particular. Skip your daily delves for 3 days if you have limited time to play. Run at least one GAP to get the best out of the pity timer on vault keys.
Android and Steam share the same servers.