How can I include figures with non-English text (and a translation) in the appendix of a research paper?
As the comments state, if the wording is of any significance to understanding your manuscript then a translation is in order. Depending on the type of figure you have several options

If your figure exists in editable digital form, you can see if actually changing the wording is possible. Even better if the format is a vctor graphics is to redraw the figure completely.

If your figure is a bit map, you could ad labels to the figure and provide translations in the text or figure caption (preferably).

Clearly the possibilities vary with the format of the original but it will be important to make the figure as understandable as possible for people not familiar with your native language.