UnicodeRangeとかいうので設定するっぽい雰囲気？＞＜

c# - dotnet core System.Text.Json unescape unicode string - Stack Overflow https://stackoverflow.com/questions/58003293/dotnet-core-system-text-json-unescape-unicode-string

https://docs.microsoft.com/en-us/dotnet/api/system.text.encodings.web.javascriptencoder.create?view=netcore-3.1