I just checked, they do send user agent to lemmy server.
For example
final appVersion = getCurrentVersion(removeInternalBuildNumber: true, trimV: true);
return {
'User-Agent': 'Thunder/$appVersion',
'Content-Type': 'application/json',
'Accept': 'application/json',
if (account.jwt != null) 'Authorization': 'Bearer ${account.jwt}',