At this point all of the projects mentioned in this thread (caster/talon/serenade) have some option for supporting the three main (win/lin/mac) platforms.
You can follow the Talon website in my HN profile to the Donate link (Patreon) and sign up for the beta tier then join the Slack to get access. Or go straight to the Slack and make your case for not being able to support the beta on Patreon at this time.
