Avoiding back doors is possible providing you use an open source program. This type of program is usually available in code, the user can examine the code and then compile it for their computer. If you don’t know how to compile a program, why not ask next door’s son!
You may ask "why would you need to do this". I will give just one example but I'm sure you can think of many more. Political parties in opposition. Ever party which is in has access to MI5.
Signal Messenger is such a program and can be used as a normal SMS program.
However, providing both parties are using the program, full encryption is also available. This part can be covered by WhatsApp, but remember - WhatsApp is a proprietary program and you’ll never tell if the CIA for MI5 have forced them to put a trapdoor in.
I dictated this whilst on the London Underground using the EdiVoice app. This app allows for long gaps between each bit of dictation unlike Google, but you need to speak slowly and clearly. The app also allows for teaching, if it gets things wrong. OK, this article is a little stilted but I haven’t used mechanical means for dictation for over fifty years. Hopefully I’ll get better at it!