Mine :-)

(gnus-sum-thread-tree-root            "┌ ")

(gnus-sum-thread-tree-false-root      "◌ ")

(gnus-sum-thread-tree-single-indent   "◎ ")

(gnus-sum-thread-tree-vertical        "│")

(gnus-sum-thread-tree-indent          "  ")

(gnus-sum-thread-tree-leaf-with-other "├─►")

(gnus-sum-thread-tree-single-leaf     "╰─►")

(gnus-summary-line-format "%U%R %3d %[%-23,23f%] %B %s\n”)

See https://github.com/condy0919/.emacs.d/blob/master/lisp/init-mail.el#L113-L121 for more gnus settings.