The preferred language of my dictation function now is Mandarin Chinese, that is, when I press the button of the microphone, it will give priority to dictate Mandarin. But I want to switch it to dictation Cantonese first. How can I do it?

Thanks for your suggestion! I have resolved the issue by exploring the settings.
The solution is to prioritize "Traditional Chinese (Cantonese)" in the Language & Region settings, instead of "Traditional Chinese." These are different options, as "Traditional Chinese" is meant for Taiwan, which uses Mandarin. When I set my device's Language & Region to prioritize "Traditional Chinese (Cantonese)," and then selected both "Traditional Chinese (Cantonese) - Stroke" and "Traditional Chinese - Handwriting" in the Keyboard settings, the dictation language for the "Traditional Chinese (Cantonese) - Stroke" keyboard page will be Cantonese, while the dictation language for the "Traditional Chinese - Handwriting" page will be Mandarin.
I understand that this issue might be a bit difficult for Apple users from non-Chinese language regions to grasp, but in Hong Kong, we use Cantonese and Traditional Chinese characters, while Taiwan uses Mandarin and Traditional Chinese characters. Therefore, there can be a bit of confusion regarding these two aspects.
Btw thanks again for reply, wish my reply can help other Chinese users:)

Thanks for your suggestion! I have resolved the issue by exploring the settings.
The solution is to prioritize "Traditional Chinese (Cantonese)" in the Language & Region settings, instead of "Traditional Chinese." These are different options, as "Traditional Chinese" is meant for Taiwan, which uses Mandarin. When I set my device's Language & Region to prioritize "Traditional Chinese (Cantonese)," and then selected both "Traditional Chinese (Cantonese) - Stroke" and "Traditional Chinese - Handwriting" in the Keyboard settings, the dictation language for the "Traditional Chinese (Cantonese) - Stroke" keyboard page will be Cantonese, while the dictation language for the "Traditional Chinese - Handwriting" page will be Mandarin.
I understand that this issue might be a bit difficult for Apple users from non-Chinese language regions to grasp, but in Hong Kong, we use Cantonese and Traditional Chinese characters, while Taiwan uses Mandarin and Traditional Chinese characters. Therefore, there can be a bit of confusion regarding these two aspects.
Btw thanks again for reply, wish my reply can help other Chinese users:)
As lobsterghost1 suggested, you need to switch keyboards to switch dictation languages, as far as I know.
To ask Apple to make this more flexible, you can use
hhttp://www.apple.com/feedback
Does it work if you set the keyboard to Cantonese
Thanks for your reply, if I change my keyboard to Cantonese, The Mandarin in the dictation function will disappear. However, I want to keep the dictation of Mandarin and Cantonese at the same time. I just want to give priority to the dictation of Cantonese. Thank you again.
If anyone can offer a possible solution, Tom Gewecke is our resident guru on topics like this. But I suspect you'll have to bounce back and forth between keyboards to accomplish what you're wanting to do.
Thanks for that useful info!
Do you have any problems with Text to Speech reading Mandarin instead of Cantonese? This is an issue in MacOS but I don't know about iOS.
How to change the priority language of Dictation?
