If you receive emails with Chinese/Thai/Arabic.. characters, sometimes they don't get displayed properly in Hiri on Linux. Instead, they are rendered as squares like so:
To fix this, you'll first have to install additional font packages for your system which provide those characters. Additionally, if you're running Hiri as snap, you might need to update your snap system.
Make sure you have the fonts
This varies between systems, so you'll have to consult the documentation for your Linux distribution. For example, to install Chinese font:
sudo apt-get install fonts-wqy-zenhei
For Ubuntu, you can find the fonts list here.
Make sure you're running snapd >= 2.29
If you're running Hiri as snap, you will have to update to the latest snapd version. To check which version you're running:
If 2.29 isn't yet available for you system, you will have to install the beta package:
snap install core --beta
When you restart Hiri, the characters should appear.