Add another font?

 I keep Photopea open in another browser tab. PP has a large selection of fonts to begin with, but you can add more.
 

Make a text layer, write whatever it is you want in the font of choice, and make it the desired color (Miro uses hex so it’s easy to pick your color and bring it to Photopea). Delete the background layer, hit Control A to select all, Ctrl C to copy, and then jump to Miro. Paste it; it will be transparent if you only used that layer and deleted the background layer in your image. Resize as you like -- it helps to start with a font size that’s proportional to the area you’re working in in Miro. 

The text will now be an image in Miro, which presents some limitations but also some opportunities. Note that opacity doesn’t translate, as currently there’s not an opacity setting for images in Miro. That can be gotten around by using a background color in Miro, and setting your text color close to the background color so it appears faint.

Finally, from a best practices standpoint, the standard fonts we use in regular communication text in English are already included in Miro. For text blocks, no one should really be deviating from the standard fonts much, as fancy fonts are hard to read and less accessible in general.  Not having localization of language is a problem, and something Miro should address sooner rather than later. But that’s different than a font issue for aesthetics, which is mostly what people here are asking about.

Use fancy fonts for titles but not for your text.