Home Assistant 0.114.3, modem Huawei E3272
I set up integration “SMS notifications via GSM-modem” work fine. But there is a problem. If i send text message in English all ok. But if i send text message in Russian it comes with a broken encoding.
How setup encoding in this integration?
I have the same issue 
This is not the encoding issue - " ? ", means that system does not know this symbol at all, so it is more likelly Locale issue. Are you running Docker container?
No, it is an encoding issue.
From code, the sms integration does not support sending unicode characters, so the available character are limited to so-called " GSM 7-bit Default Alphabet", which is basically Latin-1
pretty sad, mate. Tools loke gammu handle unicode characters with ease…
Can someone test changing this parameter to true with their environment and report back. If nothing bad happens then please submit a PR. I dont have a great deal of time and this is a community effort, anyone can participate. 
PR opened, please review:
Support Unicode in SMS messages by ocalvo · Pull Request #56468 · home-assistant/core (github.com)