You have to copy carts to TIC80 application folder, use "folder" command to find it. Unfortunately, the latest Android does not allow you to copy files to the application folder, so we are trying to find a solution.
Viewing post in Add .tic files as supported by the android app
I was just trying to figure this out myself and put a suggestion on https://itch.io/t/1818926/where-do-i-put-carts-on-android#post-7132064
The app should have an Android intent that lets other apps, such as a file manager or the web browser after download, share a .tic file to it so you can open files that way. Not sure if the app also needs file system permission with that or if the intent system just passes the object without necessitating that (probably?) Or the app could have file system permission and create the TIC-80 folder at /storage/emulated/0/TIC-80 instead. That way users can copy files from another machine and play them.