Hi, For the record, the absence of kanshictl was previously raised in https://bugs.debian.org/1026463 but self-closed with a comment about varlink possibly not being in the best shape for inclusion in Debian.
I'm personally not decided for or against packaging varlink in Debian at this point. I think I might try following up with kanshi and/or varlink upstream to inquire more about the situation. I'll look into either packaging varlink and adding kanshictl, or otherwise amending man kanshi(1) to drop references to kanshictl(1) to avoid confusion. Also FWIW, per https://todo.sr.ht/~emersion/kanshi/104 upstream kanshi didn't seem interested in exploring other options in place of varlink.
