On the March 7th I participated in Guix Patch Review Session:
https://libreplanet.org/wiki/Group:Guix/PatchReviewSessions2024
Thanks to Romain Garbage (https://gitlab.inria.fr/rgarbage) who helped me with "git send-email" I'm now figured out how to use this command properly to send patches for GNU Guix. My first patch that was sent this way:
https://debbugs.gnu.org/cgi/bugreport.cgi?bug=69635
Before I used to send my patches as attachments to plain emails I wrote in Emacs GNUS.