Yes. MySignature is compatible with all major email clients, including Mozilla Thunderbird.
MySignature email generator makes it simple to create exclusive email signatures for your Mozilla Thunderbird account.
Here is a short and easy guide on how to make an email signature to your liking.
Mozilla Thunderbird is available in 59 languages
Its 1.0 version received 500,000 downloads in 3 days
It runs on Linux, Windows, and MacOS