Choosing a dev. board ESP 32 S3 ProS3 or Arduinos - IOT, Air quality sensors,Temperature,GPS,Touch Screen, Battery Hi everyone. Need some advice.

If you stick with Arduino R4, address TFT and serial conflicts by reducing reliance on SoftwareSerial. You can also  switch to I2C versions of peripherals.

For the TFT, you'll simply have to search out where the wiring_private.h file is, and ensure that the compiler can see it. There's no shortcut here; if google has not helped, then you'll need to do the work of locating that file, or looking to see what that file is used for, and see if you can modify the TFT driver code to not require it. The Arduino Uno R4 is quite different from the other Arduino boards, so you could also consider just buying a different Arduino.

Regarding serial ports, you'll eventually learn some techniques to address this, but if you're in a rush, maybe it's good to stick with what's working, and simply remove the GPS module. It's likely not needed for the device (you can always obtain the time via WiFi). The display might not serve much of a purpose either, if people can access the data using other methods. But it seems like removing the GPS module would solve the problem with little impact.

Some random techniques you could investigate (but be prepared for it to take some time if you're new to this) could be to implement your own PM2.5 or GPS driver code, i.e. not rely on the ready-made one which seems to require a member function that doesn't exist with the R4 uno. Another technique is to simply only use one device at a time, i.e. create and delete the object after use. This may or may not work. You could multiplex the interfaces with a bit of hardware for that. If you move to different hardware, the lowest-impact method will be to use another Arduino board, and just accept the price difference for your prototype. Or use I2C peripherals as bidrohini mentions. 

In summary, there's lots of approaches you could try, a few listed above. But the simplest is to remove the peripheral that you don't need.

Perhaps a Raspberry Pi Pico has enough serial capability.

A RPi Pico only has 2 hardware UARTs (and 2 HW I2Cs).
Just had an idea to map the interfaces to different IO pins at different times. If that works the limit would be the # of IO pins available.

 nazcuriosite My guess is that you'll experience the same challenge with the ESP32 as you do with the Uno R4.  If the IDE can't find it for one, it won't find it for the other.

You may want to consider keeping the Uno R3 as it isn't as power hungry as the R4.

The Earle Philhower port of the Pico to the Arduino IDE seems to allow multiple PIO UARTS, and there are Pico software serial libraries that can be used as well.

Agree, since the OP is a beginner, it's going to be difficult to do much else, apart from using what is already known to work, i.e. Uno R3.

If the only reason they moved to Uno R4 was to use the WiFi for IoT purposes, then they don't have much choice other than remove the peripherals that are not working for them, or use known working items with that combination.

Moving to a different board much different from Uno R3 will simply result in the same issue or other issues.

A TFT and GPS may not be entirely necessary if all they want is WiFi, so are candidates for removal. It might not be ideal, but that's the price to pay when you're a beginner; it takes time, one can't just launch into a project with many elements and expect it all to work. There was a time for many of us I'm sure, when first projects were literally just lighting a bulb with a wire and a battery. But it had to be done.

Yes, you are correct. I always forget the PIOs, they count as hardware too. 

shabaz   I'm back to that point with the Arduino Opta.  In all fairness, I'm not working on it like I was doing a Roadtest - but I certainly don't remember as much as I thought I would.  I'm back to one function at a time.  Solve that.  REM that block out.  Work on the next block.
Lather. Rinse. Repeat. 

I find I'm the same. A lot of things these days feel complex enough that if I'm not working on it daily, then it's going to be a major uphill struggle next time I want to use it.

I'm sure from experience we all take notes (for me it's usually in the form of a Word docment per "thing" I'm working on, and often those notes become a blog if it's in a useful state) to speed up things the next time, but sometimes even that doesn't entirely help, and it's back to basics to start building the knowledge again! Sometimes, I just don't have that persistence, though, especially if a manufacturer has made things unnecessarily difficult, for instance.