This is reproducible for me with the packaged ghc (/usr/bin/ghc) for darcs screened as well as the packaged /usr/bin/darcs. The symptom is:

> /usr/bin/darcs push darcs-unstable@darcs.net:screened
patch ab4da673253288bf284bf7b55a4c647fff9428b5
Author: Ben Franksen <ben.franksen@online.de>
Date:   Mon Aug 28 15:36:05 CEST 2023
  * rollback accidentally recorded parts of c4d15858
darcs: mmap 4096 bytes at (nil): Cannot allocate memory
darcs: Try specifying an address with +RTS -xm<addr> -RTS
[1]    64023 segmentation fault (core dumped)  /usr/bin/darcs push darcs-unstable@darcs.net:screened

I am currently not in the mood to go through the hoops to create a bug report on launchpad, but will perhaps do so in the following days (unless someone else does it).