added it as directed above. Still weird behaviour of the Atom Matrix on FW 1.13.2.
Here is the log:
I print out "submitted to aws" after the publish block in the loop.

APIKEY: xxx
submitted to aws
[17797] MQTTException -> 128
reconnect start ...
reconnect finish ...
submitted to aws
submitted to aws
submitted to aws
submitted to aws
submitted to aws

Well there is an improvement as you are no longer getting the [24577] MQTTException -> [Errno 9] EBADF
Which means the Atom is now working

Error 128 means that it tried to subscribe to the AWS topic before the connection was made.
If you make a subscribe and a call, according to your log it should be present.

add a 5 second delay after the AWS start.

My summary as of Feb 2024 and Firmware 1.13.2 and UIFlow 2.0 (Alpha 29):

Forget all new devices that are supported by UIFlow 2.0 only (e.g. *S3) and the small ATOMs if you wanna do AWS IoT stuff. Hope you find this before you bought too many devices...

APIKEY: xxx
submitted to aws
[17797] MQTTException -> 128
reconnect start ...
reconnect finish ...
submitted to aws
submitted to aws
submitted to aws
submitted to aws
submitted to aws

Add
import gc

to the import code and then at the beginning of the loop add

gc.collect()

This forces garbage collection in micropython on each pass emptying the memory on each loop.

Look up Micropython Garbage collection function for more information on this.

unfortunately I can't get into my AWS account and so haven't been able to test but it could be that you have genuinely found an issue in the Atom firmware.

ATOM Matrix
Firmware: 1.13.2

Both in Internet and App mode

-- Code --
from m5stack import *
from m5ui import *
from uiflow import *
import wifiCfg
import time
from IoTcloud.AWS import AWS
from libs.json_py import *
import unit

rgb.set_screen([0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0])
tvoc_0 = unit.get(unit.TVOC, unit.PORTA)

CO2 = None
TVOC = None
H2 = None
Ethanol = None

wifiCfg.doConnect('Guest', 'xxx')
wifiCfg.autoConnect(lcdShow=False)
wait(5)
aws = AWS(things_name='CO2SENSOR', host='xxx.iot.eu-central-1.amazonaws.com', port=8883, keepalive=500, cert_file_path="/flash/res/certificate.pem.crt", private_key_path="/flash/res/private.pem.key")
aws.start()
while True:
CO2 = tvoc_0.eCO2
TVOC = tvoc_0.TVOC
H2 = tvoc_0.H2
Ethanol = tvoc_0.Ethanol
aws.publish(str('m5stack/bla'),str((py_2_json({'CO2':CO2,'TVOC':TVOC,'H2':H2,'Ethanol':Ethanol}))))
print('submitted to AWS')
wait(5)

— Serial Log --

submitted to AWS
[10490] MQTTException -> [Errno 9] EBADF
reconnect start ...
reconnect finish ...
[14075] MQTTException -> [Errno 9] EBADF
reconnect start ...
reconnect finish ...
submitted to AWS
[17541] MQTTException -> [Errno 9] EBADF
reconnect start ...
reconnect finish ...
submitted to AWS
[20998] MQTTException -> [Errno 9] EBADF
reconnect start ...
reconnect finish ...
[24577] MQTTException -> [Errno 9] EBADF
reconnect start ...
reconnect finish ...
submitted to AWS

In App mode you must add the wifi configuration and setup blocks to the code for the Wireless connection to work.

Sorry, I have been battling a chest infection and so wasn't able to clearly see the solution. While I did write the crappy book on IOT found on amazon, things have changed and I am already writing an update while working on the other deep guides.

At one point I had to store the Public and private keys generated by amazon along with the cert on the client to get a connection.

Try setting Keep alive to 500.

Will need to see the full code to work out what's happening.

AWS is constantly changing so my guides are probably out of date and need updating. I hate AWS as it a Pain.