GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, GTK+ Version 2.24.33, cairo version 1.16.0) of 2022-07-26
Tested also with `emacs -Q', so this is not a problem of my configuration.
1. Open (a slow) remote connection, with TRAMP
2. Run M-x find-dired RET, arguments not important
3. Internal error "Wrong type: processp, nil" appears
Debugging suggests that it happens in `find-dired-with-command' when calling `set-process-filter'. Apparently the asynchronously started shell command started ~30 lines above counts as having finished (?) by then.
Paul