Dear Maintainer,

The /etc/init.d/console-setup.sh startup script does not change
 the system console font if the plymouth graphic splash screen is
 enabled at startup.

Still reproducible on testing.

Here is the deal:
Console setup is supposed to rely on cached scripts in /etc/console-setup (copied to initramfs). But plymouth starts in initramfs, occupies tty1, which causes setupcon to detect graphical mode and skip tty1.
When scripts exist in /etc/console-setup, conditions in /lib/console-setup/console-setup.sh basically skip running setupcon if console-setup.service is launched first time during boot.

To fix this:
1. add plymouth-exit.service to After= in console-setup.service
2. add plymouth exit detection to console-setup.sh

--- /lib/console-setup/console-setup.sh	2023-02-09 01:33:51.198998809 +0300
+++ /lib/console-setup/console-setup.sh	2023-02-09 01:34:10.826464995 +0300
@@ -16,6 +16,10 @@
               -nt /etc/default/keyboard ] || do_configure=yes
         [ /etc/console-setup/cached_setup_terminal.sh \
               -nt /etc/default/console-setup ] || do_configure=yes
+
+        # if plymouth-exit.service was launched and registered as active,
+        # plymouth has released tty1 for us to fix
+        systemctl is-active -q plymouth-quit.service && do_configure=yes
         ;;
 esac

Check if systemd is present to avoid errors if it is not.

--- /lib/console-setup/console-setup.sh	2023-02-09 01:33:51.198998809 +0300
+++ /lib/console-setup/console-setup.sh	2023-02-09 01:59:48.786418782 +0300
@@ -16,6 +16,13 @@
               -nt /etc/default/keyboard ] || do_configure=yes
         [ /etc/console-setup/cached_setup_terminal.sh \
               -nt /etc/default/console-setup ] || do_configure=yes
+
+        # if plymouth-exit.service was launched, this means
+        # plymouth released tty1 for us to fix
+        command -v systemctl >/dev/null && \
+              [ $(ps -p 1 -o comm=) == "systemd" ] && \
+              systemctl is-active -q plymouth-quit.service && \
+              do_configure=yes
         ;;
 esac


Other than that I do not know how to quickly detect exited plymouth and properly order console-setup launch in a SysV boot.
Maybe modify /etc/init.d/console-setup.sh to hold while plymouthd is running (with a timeout).

A bit more refined variant without ps:

--- a/lib/console-setup/console-setup.sh   2024-02-09 17:45:38.000000000 +0300                                          
+++ b/lib/console-setup/console-setup.sh 2024-02-14 01:15:24.413177808 +0300
@@ -16,6 +16,16 @@
               -nt /etc/default/keyboard ] || do_configure=yes
         [ /etc/console-setup/cached_setup_terminal.sh \
               -nt /etc/default/console-setup ] || do_configure=yes
+
+        # if plymouth-exit.service was launched, this means
+        # plymouth released tty1 for us to fix
+        if [ -r /proc/1/comm ] &&
+              [ "$(read -r INIT < /proc/1/comm ; echo "$INIT")" = "systemd" ] &&
+              command -v systemctl >/dev/null &&
+              systemctl is-active -q plymouth-quit.service
+        then
+              do_configure=yes
+        fi
         ;;
 esac

If plymouth password prompt is used during boot (i.e. root volume decryption from initramfs), just the patch above will not work, also need to add plymouth-quit.service to 'After' property in console-setup.service