@ enjoyneering
As Don says the IDE library manager already calls up a library of that name so it is unlikely it will get added as is. There are also about 5 other library variants with the same name. Forum posts here show that causes a lot of grief to newbies as the other libraries must be weeded out to avoid conflicts and it is not clear what library a Newbie is using when they post a sketch.
I have a reluctance to adopt any libraries with identical names to one I already have as this can "break" some of my existing working sketches.
I have taken the liberty of cloning and batch renaming the library to "PCF8574_I2C_LCD" so I can test it alongside other libraries LCD I2C libraries. If anyone else want to take the same approach then the copy is temporarily here.
Note however that this copy will not be kept up-to-date and therefore should be used with caution. I will be deleted at some point.
To use other I2C addresses (other than those built into the library) I had to use type casting (which is inconvenient) e.g.:
#include <PCF8574_I2C_LCD.h>
PCF8574_I2C_LCD lcd( (PCF8574_address) 0x3F );
Once that was done one of my existing I2C clock+temperature sketches worked fine though the sketch FLASH size did increase by ~500 bytes for some reason compared to the LiquidCrystal_I2C library the IDE library manager calls up. (Not a big problem though).
The library looks very neatly written. Good job!