There's a fork of QK called QUIK if you like that app but want something more updated. I personally use fossify though.
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Just to thow in the mix. I think QKSMS is dead, or atleast rarely updated.
Another fork is providing updates via https://github.com/octoshrimpy/quik
I still use QKSMS coz I CBF migrating till i get a new phone.
So it seems qksms isn't being maintained, but also I've been using it since signal dropped sms support, and it's been zero problems for me
To my knowledge QKSMS/Quik tries to do something way bigger, like multiple protocols.
I recommend DekuSMS. They have AES encryption for people both using the app, and it just works well.
I've never used Fossify SMS, so I can't really comment on it, but I've been using QKSMS as my default messenger for a few years now and I quite like it. The feature that keeps me on QKSMS is exporting and importing text messages. It's a godsend when you're changing phones.
With Fossify SMS you can also exporting and importing text messages.