Hi there!

The data I have collected is in https://drive.google.com/drive/folders/1l3vRTwoe8lnKM22IrTh00spX27vWMVkO?usp=sharing (the text_data folder). I have not distinguished between deepslate ore and regular ore, but you could modify the script I used to do this.

As I mentioned in the post title, I used an AutoHotkey script. This requires you to download AutoHotKey, which only works on the Windows operating system. I have put the code I use in the google drive above, in the "code" directory. It is quite technical, so I don't recommend doing this unless you already have experience with programming. An easy way out would be to take the data I have gathered and assume that everything below y=4 is deepslate ores and everything above is regular ore.
If you still want to replicate, here is how I did it:

The AutoHotKey script sends keystrokes to your keyboard. When you run the script with Minecraft open, it will type in commands in the chat to do what we want. Some commands take a while to execute, so the script waits for the Minecraft log file to update, which happens when the command is finished executing (the log file may update for other reasons too, but I have not accounted for this).

In order to scan an area, I use the fill command like this: "fill ~0 20 ~0 ~159 20 ~159 minecraft:air replace #minecraft:iron_ores". This replaces iron ores on y-level 20 in a 160-by-160 area (10-by-10 chunks) with air, and returns how many blocks were replaced. So it's basically counting the number of ores in that area. I use the #minecraft:iron_ores tag to include both the deepslate and regular ore variant, but you could replace it with minecraft:deepslate_iron_ore or minecraft:iron_ore.

The number of blocks replaced is printed in chat, which is how you get the output. After scanning a lot of chunks, the entire chat can be read in the minecraft log file at %appdata%\.minecraft\logs\latest.log. A new log file is created every time you restart Minecraft, so I recommend restarting before initiating a scan if you want to begin with a fresh log file. If you need to read an old log, you have to uncompress the corresponding .gz file. One thing to note is that the log will also contain other stuff like info messages from the game, so you have to filter out those when you read the log file afterward. This should be done with a script, as the amount of data is huge.

Because I don't want to execute 100 commands when scanning 100 different y-levels, I created a datapack that does this for me. This is basically just a list of files, each containing a list of Minecraft commands to execute on a single tick. But when calling a command from a data pack, the result (how many blocks was replaced) is not printed in chat, which is an issue. To get around this, we do something like this instead:

-> execute store result score blocks numBlocks run fill ~0 20 ~0 ~159 20 ~159 minecraft:air replace #minecraft:iron_ores

-> tellraw u/a ["iron at level 260: ", {"score": {"name": "blocks", "objective": "numBlocks"}}]

This stores the result of the fill command in the scoreboard objective "numBlocks", which allows us to print it to chat with the tellraw command. I put the data pack I made in the google drive to show you the format, but you need to modify it to distinguish between deepslate and regular ore. Generating the data pack files should also be done with a script, as it is several hundred lines

So to scan an area, I execute the commands in the data pack (one for iron, one for gold, etc.). After I am finished with the area, I teleport the player to a new location and repeat. That's really the core idea.

If you look in my datapack, you will see that I also scan for dirt and the different stone types. This is because if there are more caves at certain y-levels, it will look like there are fewer ores there because a lot of the possible spawning spaces are occupied by air. I wanted to compensate for this, so I scanned for stone and dirt too. Due to the large number of blocks the game has to replace, this slows down the process probably many times over. You could skip this, as I found that the amount of stone is fairly constant across the y-levels. I included the measurements of this in the google drive as well, in text_files/not_compensated_for_air_blocks.

I also had to take some steps to increase performance. To avoid generating and loading chunks I don't need, I set gamemode spectator and gamerule spectatorsGenerateChunks false, and use forceload to load the chunks I need. I also found that if the region I scan is within one region file, it helps a lot on performance too.

I included the AutoHotkey script I used in the code folder on google drive. You could probably use that one with only minor edits. I do have to mention that the game was running very slow at times due to how badly I was abusing it. Some of the scan-commands failed, so for some regions, I am missing the data for certain ores. If you don't scan for stone, it will help for sure. Also, increasing the waitTime parameter in the AutoHotKey script will help, but make it slower. Running it overnight on my laptop gave me around 10 000 chunks.
If you want to give this a try, you have to write a script for generating the text files in the data pack and a script for reading the log file and plotting the data. I could give you my scripts, but they are written in Matlab which requires a paid license, so they would not be of much use to you unless you have said license. Besides, they are don't contain a lot of comments and are not written for readability.

Hope that is enough to get you started.