I have been able to cobble together a workaround:

1. Write the data frame that you want to append as a temporary table (temp) in the SQLite database file.

2. Append it to the target table (target) using the SQLite statement:

   insert into target select * from temp;

3. Drop temp.

This runs quite fast, presumably thanks to SQLite being well optimized.

I have been able to cobble together a workaround:

1. Write the data frame that you want to append as a temporary table (temp) in the SQLite database file.

2. Append it to the target table (target) using the SQLite statement:

   insert into target select * from temp;

3. Drop temp.

This runs quite fast, presumably thanks to SQLite being well optimized.

ADDENDUM:

You can indeed append a data frame to a database table using dbWriteTable, with the option append=TRUE. I have tested this against my workaround described above and, surprisingly, the workaround runs almost 40% faster than dbWriteTable.