What about this article?

--Describes how to use the Caps Lock key as the Ctrl key with the xmodmap command. -= Replace the Caps Lock key with the Ctrl key. --Cinnamon or GNOME3 can be realized with standard functions, but it seems that Xfce cannot. ――Please let me know if you know. --Operation check environment - Fedora 31 64bit

TL/DR; --Install Xodmap. --It should be old software, so it should be most X Window environment. --Test by writing key bindings in ~ / .Xmodmap. --Set to write in .bashrc and read automatically at login.

procedure.

Install xmodmap.

Fedora

sudo dnf install xmodmap

--With yum up to CentOS7. (Which of fedora is fine, but when yum can't be used ...)

sudo yum install xmodmap

Test by writing key bindings in ~ / .Xmodmap.

Keymap settings. (The file name can be anything.)

cat << '_EOT_' >> ~/.Xmodmap 
clear lock
keycode 66 = Control_L
add control = Control_L Control_R
_EOT_

--On my laptop, Capslock's keycode was 66. --Check around xev. - dnf install xev --Tap xev to find out the keycode. --After hitting xev on the terminal, if you press the corresponding key while the xev screen is active, you can check the key code as shown below. --As shown in the capture below, the keycode for Capslock is 66.

Keymap setting read test.

xmodmap ~/.Xmodmap
echo $?

Set to automatically load keymap settings when logging in.

cat << '_EOT_' >> ~/.bashrc 
xmodmap ~/.Xmodmap
_EOT_

Check if there is moss by reading .bashrc.

source ~/.bashrc 
echo $?

Digression

--Since the Alt key does not respond on my laptop, the conversion key, non-conversion key, and katakana / hiragana key are all operated as Alt keys as shown below.

cat ~/.Xmodmap
clear lock
clear mod1
keycode 100 = Alt_R
keycode 101 = Alt_R
keycode 102 = Alt_R
keycode 66 = Control_L
add mod1 = Alt_R
add control = Control_L Control_R

――At first, I used to use Windows-like cinnnamon, but over time the machine specs couldn't keep up. --LXDE is also comfortable, but there is a bug that forces the US keyboard to be recognized. --Xfce comfortable. ――I feel that some of the shortcuts are unique ...

reference

https://wiki.archlinux.jp/index.php/Xmodmap

Use the xmodmap command to operate the Caps Lock key as the Ctrl key.