For me, a C# developer by trade, this is easily solved with a one command C# call. It’s possible you already have dotnet 6 or 8 on your distro as there are many C# Linux apps now.
https://www.nuget.org/packages/System.Text.Json/9.0.0-preview.4.24266.19
I don’t knowvwhat mtls is, but Joplin has mostvof what you want. It does not have card layout native, but there might be a plugin for that.