When I used Debian 10, whose desktop environment was Xfce4 and login manager was LightDM accompanied with its GTK greeter, I had to enter my username every time I started my computer. It might have become more convenient.
After all, I found how to configure it. Edit lightdm.conf:

$ sudo nvim /etc/lightdm/lightdm.conf

to deactivate greeter-hide-users:

- #greeter-hide-users=false
+ greeter-hide-users=false

Then the greeter kindly showed my default user on boot.