Hello everyone,
After also searching the web and finding no other information that I could figure out, people speaking in riddles and posting videos that didn't help, I did manage to get this converter working. THANK YOU LARGEMOOSE421!
I have the EZ Flash Omega Definitive Edition, I did the Official Firmware Update, then added the Official Cheats and Imgs from the EZ Flash website. Then I upgraded to the SimpleDE custom firmware that I found on these forums somewhere. However, I doubt you need that custom firmware in order to get these cheats working. Here is how I got it to work.
1) Figure out which game you have (can usually find this via the EZ Flash Menu, for example, Final Fantasy Tactics Advance (USA) is the 1141.cht for me, and if you have the Official EZ Flash Cheats then it should be the same for you.
2) On your computer, plug in your Micro SD, and open the correct .cht file with Notepad. It should be located in the CHEAT > Eng > numbered folder (1000 for me).
3) Open the gamehacking.org page for GBA, find your game, and use the FILTER option on the page to set it to Action Replay MAX, so that ONLY those AR MAX codes will display, the Converter will only work with these that I'm aware of.
4) Find the code, and copy only ONE LINE at a time. Example, FFTA's code to give AP at the end of battle, the AR MAX code listed on that site is:
0221F514 00001188
5) Open OP's Converter: ar2cht.netlify (note, that if you are using Chrome, you can actually install an OFFLINE version of the app, it'll be at the end of your URL address bar, near where you can add a bookmark)
6) On the Converter page, add a Cheat Name if you want, then paste the first line of code into line 1. It should automatically give the conversion underneath. For FFTA, the converted code for AP is:
[Give AP]
ON=1F514,88,11
7) If you copy that into the proper spot in the 1141.cht file (in with the other codes) using Notepad, and save it to your Micro SD card. It will work. So feel free to use that code since I've done the work on it.
NOTE: I kept forgetting that when you are IN THE GAME, you need to press L+R+Start to bring up a hidden menu and turn CHEAT ON. This goes for all games.
8) If you have a multiple line code, you will see the blue ADD LINE TO CHEAT button on the Converter. Go back to the gamehacking.org page, copy the SECOND LINE of code, then paste it into the SECOND BOX on the Converter. You will need to do this for every single line, one at a time.
NOTE 2: I HAVE NOT DONE MULTIPLE LINE CODES YET, so I cannot say that they work. However, with having my one line of code converted and working perfectly, I am confident that Step #8 is the way the OP intended the tool to be used.
I hope this helps the next person who finds the built in cheat codes lacking x.x
I did also send an email to EZ Flash earlier to ask how to convert all the Codebreaker, GShark and ARMax codes, juuusstt in case they decide to tell someone. If they do, I'll post about it here. Not expecting anything though since I doubt I'm the first to ask.
I CANNOT POST IMAGES OR LINKS DUE TO NEW ACCOUNT
Edit: OP, if you found this helpful, feel free to use this or a modified version of this for the tutorial page. I just want to help people out.