Changing font asset and material at the same time for a language

Yes,
You can change the font, the material or both.

It can be done by one of two ways:

1- Add a secondary term and set it to TMP Font or Material type. Then set your font assets or materials per language.
inter-illusion.com/assets/I2Localization...FontperLanguage.html
Notice that when using this approach, if you set a font, I2 Localization will select the first material that matches that font as well.
And if you are setting a material, then, the plugin will find the font corresponding to that material and apply both.

or

2- In your translation text, set the name of the Font/Material as a tag at the beginning of the text
(e.g. instead of "This is an example", add "[MaterialName]This is an example"
That allows you to define a font to set (using the Secondary Term) and the specific material you wan to use.

Hope that helps,
Frank

Can you confirm that with the first approach, I need to have 2 Localize components on the Text object?

Now, you don't need two localize components.

Lets say that you have two fonts ("Arial SDF" and "Roboto SDF")
Then, you have two materials for each of them:
"Arial SDF - Shadow" and "Arial SDF - Outlined"
"Roboto SDF - Shadow" and "Roboto SDF - Outlined"


If you want to change a label to use "Roboto SDF" with the "Roboto SDF -Outlined" material,
then:

Add 1 Localize component
- Set the main term to be whatever you want the label text to show
- Set the secondary term to a term of type Material referencing the "Roboto SDF - Outlined"

When the localization happens, the plugin will take the material, find the font matching that material and change the label font and material to those.

Now, if you just want to change the font and select the default material for that font,
Then, set the Secondary term to a term of type "TMP Font" pointing to "Arial SDF". The plugin will ask TMPro for the default material for that font and apply it.

Either way, its just 1 localize component if you want to change the font, material or both.

It would be great if the Localize component just has a list of Terms and what each Term does is up to their Type.

I agree.
I have in my todo list a detailed task to redo the way how the terms work to avoid to force two term in a localize component, and greatly simplify it.
But given that all cases can be solved by using the current system, there seems to always be something with a higher priority that pushes that task to the backlog.

Hopefuly now that E3 is over, I should have more time to complete more of the high priority taks and clear the list!!