Still the new version of the linux client, which is now out of beta, has no permanent killswitch, and as others have complained about no secure core, no option to minimise on startup, no split tunnelling etc.
The old version is very buggy, but I do have a script that made handling it less painful, and it at least was not lacking essential features. Where can I still get the old version please?
It has been said already that split tunneling is not technically possible with the NM backend and secure core is already implemented. I guess they’re already working on perma KS as that was their next goal as we were told.
Check their GitHub page for previous versions
You have to download stable release 1.0.3 from their repository
Great, so still unusable then.
Not having a permanent killswitch is as good as having no kill switch, unless temporary security and privacy will suffice.
You make no sense at all 
just because it does not fit your threat model it doesn’t mean it not usable. Also in such a case you should be setting up your own KS if you’re acutely worried about 3rd party software.
What does not make sense is someone wanting the security and privacy benefits of a VPN some of the time.
I am not acutely worried, I would just like the VPN to be functional.
Are you new to VPNs?