As a software developer, I completely understand the problems involved with trying to build--let alone maintain--a Linux client. For anything. Yep, it costs money, not enough user base, blah blah blah. Heard it before, been there done that, can't disagree.
So instead of creating a full-on Linux client, why not BEEF UP THE WEB VERSION. I've been using it for a while, after abandoning things like NixNote and other similar attempts. I'm mostly happy with it... until I lose Internet for a second or two.
I'll pay to get premium access if the damned thing works offline. Use offline storage. Only support modern browsers. All that stuff. Just make it work so I can type up some stuff when I lose Internet, and let it sync-up when I regain access.
I've been using the web client for a long time. I'm super happy with it. I just now very nearly went and paid the subscription fee, even though I'm broke. But then.. why? Do I get the offline storage in my browser? I don't want to pay for something that I have to boot into Windows or fire up a Windows VM to use.
TLDR: make the web app suck less if the 'net connection goes away.