Ah you just reminded me, I remember Tttris / Titris being one of the better free open source Tetris clones on Android way back. No ads, no need to be online, just a good standalone Tetris clone for Android. I still have the old .apk, might be the same as the last one published to F-Droid https://f-droid.org/en/packages/com.seavenois.tetris/ but like you said eventually stopped being updated & isn't compatible with current Android phones nowadays.

Now you got me thinking about this again, wish I had a good suggestion. Will be following this post, maybe other people know about some other good ones.