If GSM Arena's page on the OnePlus 12 is correct, it can only run ARM64 native code: the processor cores in its Snapdragon 8 Gen 3 SoC can't run in 32-bit mode. For more about this, see here.
If the app requires 32-bit native code, which seems to be the case from your question, then you are stuck: your 'phone can't run that code. Rooting would not help at all, your hardware can't do it.
It isn't impossible, in principle, for someone to write an emulator to run 32-bit Android native code on 64-bit Android, but I don't know of it being done, and it would be complicated. Some Xiaomi devices come with the "Tango" binary translator which allows then to run 32-bit native code, but that isn't generally available as far as I know.
The easiest solution would be to acquire a 'phone that can run 32-bit native code. Those are still around, but they won't be forever.