and backup methode create an sql script with one INSERT statement for EACH ROW...i think that is the problem...
because when using SQL SCRIPT created with SQLITE MAESTRO the restoring is very fast ..because the script contain ONLY ONE INSERT statement for the whole table.
Part of sql script created with Backup method

Part of sql script created with sqlite maestro software.

here is my example test project.
https://mega.nz/file/Fch0xILL#U49lQy-XM ... e0Z2JNbr20