*ERROR*: No applicable method: frame-creation-function, ((client . #<process server <15>>) (environment "_=/usr/local/bin/emacsclient" "TERM_PROGRAM=iTerm.app" "__CF_USER_TEXT_ENCODING=0x1F5:0x0:0x0" "OLDPWD=/Users/jacobfaibussowitsch/NoSync/petsc" "MFEM_DIR=/Users/jacobfaibussowitsch/NoSync/mfem" "REMOTE_USER=jacobfaibussowitsch" "PATH=/usr/local/opt/ccache/libexec:/usr/local/opt/gnu-sed/libexec/gnubin:/Users/jacobfaibussowitsch/NoSync/petscpackages/bin:/Users/jacobfaibussowitsch/bin:/usr/local/bin:/usr/bin:/usr/sbin:/bin:/sbin:/usr/X11R6/bin:/usr/local/sbin:/Users/jacobfaibussowitsch/.cargo/bin" "PS1=[darwin-c-debug]\\[\\][\\[\\]LOC\\[\\]\\[\\]]\\[\\]\\[\\033[36m\\]$(parse_git_branch)\\[\\033[m\\]@\\[\\033[33;1m\\]\\w\\[\\033[m\\]$ " "XPC_SERVICE_NAME=0" "SHLVL=1" "DISPLAY=/private/tmp/com.apple.launchd.7c2LVKTrQr/org.xquartz:0" "LC_TERMINAL_VERSION=3.4.9beta1" "PETSC_ARCH=arch-darwin-c-debug" "olcftutorialdir=/ccs/hom

3. $ emacsclient -c

Possible culprit(?):

This recent merge https://git.savannah.gnu.org/cgit/emacs.git/commit/?id=6535fd1fa9ac21238a168916249ac59677a6118e introduced

diff --git a/lisp/frame.el b/lisp/frame.el
index 9b3d120598..8c05ad2fe5 100644
--- a/lisp/frame.el
+++ b/lisp/frame.el
@@ -36,7 +36,11 @@ as its argument.")
(cl-generic-define-context-rewriter window-system (value)
;; If `value' is a `consp', it's probably an old-style specializer,
;; so just use it, and anyway `eql' isn't very useful on cons cells.
- `(window-system ,(if (consp value) value `(eql ,value))))
+ `(window-system ,(if (consp value) value
+ ;; WARNING: unsure whether this eql expression
+ ;; is actually an eql specializer.
+ ;; Bug #47327
+ `(eql ',value))))

Specifically the last line `(eql ‘,value). Removing the quote from value (i.e. `(eql ,value) ) fixed things on my end. Seems the warning was salient ;)

Best regards,

Jacob Faibussowitsch
(Jacob Fai - booss - oh - vitch)