Let me first say that Claws Mail is a perfectly good, light based, offline email client for Linux Mint. I love that its designed for text only which is how I access my email on Gmail.
This post is not about using Claws Mail as a dedicated email client but rather as an email tool to access backup / archived Gmails. I like using Gmail on the web, Chromebook, and Android and have no desire to use a dedicated email account for daily use. On the other hand, I don't want my Gmails on the cloud indefinately. That is where Claws Mail comes in for me.
Google Takeout allows me to download an mbox file of all my Gmails which I try to do yearly. I download this mbox file and then delete older emails from Gmail. With Claws Mail I can simply open the mbox file and have access to all those backed up emails.