I don't use lxqt but I tested it in a VM and it seems to work and look just like it did before.

list of packages updated:

lxqt
lxqt-connman-applet
lxqt-openssh-askpass
qps
compton-conf
lxqt-archiver
screengrab
qterminal
qtermwidget
pavucontrol-qt
obconf-qt
lximage-qt
pcmanfm-qt
lxqt-themes
lxqt-sudo
lxqt-session
lxqt-runner
lxqt-powermanagement
lxqt-policykit
lxqt-panel
lxqt-notificationd
lxqt-globalkeys
lxqt-config
lxqt-admin
lxqt-about
libsysstat
liblxqt
libqtxdg
lxqt-build-tools
lxqt-qtplugin
libfm-qt


Here is a VM that autologs in to lxqt

run: $(./pre-inst-env guix system vm ./lxqt-os.scm) -m 1G

(use-modules (gnu)
(srfi srfi-1))
(use-service-modules desktop xorg sddm)
(operating-system
(bootloader (grub-configuration))
(file-systems %base-file-systems)
(locale "en_AU.utf8")
(timezone "Australia/Hobart")
(keyboard-layout (keyboard-layout "us"  "qwerty"))
(host-name "jiu")
(users (cons* (user-account
(name "b")
(password (crypt "b" "$6$abc")) ;; password "b"
(comment "Brendan")
(group "users")
(home-directory "/home/b")
(supplementary-groups
'("wheel" "netdev" "audio" "video" "kvm")))
%base-user-accounts))
(packages
(append
(map specification->package '("nss-certs"))
%base-packages))
(services
(append
(list (set-xorg-configuration
(xorg-configuration
(keyboard-layout keyboard-layout))
sddm-service-type)

(service lxqt-desktop-service-type)
(service sddm-service-type (sddm-configuration
(auto-login-user "b")
(auto-login-session "lxqt.desktop"))))
(remove (lambda (s) (eqv? (service-kind s) gdm-service-type))
%desktop-services))))