like UNO but with more DIO and GSM Library support

Using Arduino Project Guidance
1

I'm starting a new project and I need a suggestion about the hardware to buy.

I need few more Digital Input than what the Arduino Uno can supply, so I can't use the Arduino Uno.
I need to communicate with GSM module in order to post images via HTTP POST method on my website.

Which hardware should I buy?

I was thinking to buy Arduino Due with GSM shield V2 but, even if they are electrically compatible, I read that GSM library is not supported by the arduino due.

I was thinking to use the Arduino MKR GSM 1400 but is has few digital inputs.

Which is the solution?

2

use a second UNO (nano / mini )
use an shift register input
use a MEGA
Use a Maple board ?
use an ESP32 (3.3v)
Teensy++ 2.0 (5v) 48 DIO

all are UNO software compatible so you can port over, you will need to alter pin assignments.
some offer higher resolution Analog
some have much higher clocks

3

ATMega1284 in DIP-40 package has 24 digital IO plus 8 analog pins. However Arduino doesn't make any board with this so it'd have to be a bit of a custom work. You will need to add MightyCore to the board to get support for this and have 16MHz xtal plus 2 22pF capacitors on breadboard to use this.

If this is too much trouble, there are official Mega2560 that has the same form as Due but is 5v friendly and has 54 IO plus 16 analog.

4

If you are familiar with an Uno then a Mega is likely to be the simplest way to get extra capability.

...R

5

I offer a 1284P board, with Uno style layout. 32 IO, dual hardware serial ports, 16K SRAM (twice that of the Mega), 128K flash:
http://www.crossroadsfencing.com/BobuinoRev17/

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and other form factors as well.