I don't think it's possible. The usb-db25 uses a special chip, not a usb-serial chip.
See https://www.prolific.com.tw/US/ShowProduct.aspx?p_id=6&pcid=41
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too bad... Thanks for your help! 
Hello rkl099.
I made and apk using your excellent aix SerialOTG.
The APK come work fine, but today I install the APK in Andorid 15 and the “SerialOTG1 > IsInitialized” and “SerialOTG1 > IsConnected” appear “true”, but not work really.
rkl099, can you fix the aix to work in Android 15, and say me how many money i transfer to you, please, is urgent.
Note: in Android 15, the window requesting permission to connect to devices does not appear.
Thnk you very much
Sorry, I have no Android 15 device.
Hello rkl099.
Oh, that's bad news for me. What other options can you offer me? Please tell me how much it costs so you can help me find a solution.
Thank you rkl099
You may also consider some sort of bridge ( for example a serial-to-bluetooth… )
if the popup doesn't show it maybe that:
- some other app has been defined as default
- u hv rejected permission and it stays
in both cases the only cure I know is reset all permissions for all apps in android. it is android's not otg ext behaviour.
-
the way appinventor is made, neither Rolf nor You can make necessary changes to the app manifest that would allow yr app to become default or preferred handler for otg serial. again: appinventor limitation not Rolf's.
the result is 1st tap on open fires the prompt, second opens the port successfully. -
my app using Rolf's ext works on Android 15 and 16 but definitelly Bluetooth serial is better handled by Android (even with appinventor built-in extension) and whenever I can I use bt.
good luck to You and thanks to Rolf