Edit: I edited the script to take a screenshot asynchronously, get the region with slurp, and use magickto crop it. I also multiply the values from slurp 2x to account for the 200% display scaling I have.

  #!/bin/bash 

	die(){
    notify-send "$1"
    exit 1
  }
  cleanup(){
    [[ -n $1 ]] && rm -r "$1"
  }
  SCR_IMG=$(mktemp -d) || die "failed to take screenshot"
  trap "cleanup '$SCR_IMG'" EXIT

	spectacle -nbo "$SCR_IMG/scr.tiff" &
	region=($(slurp -b "#00000000" -c "#80808080" -w 2 -f "%w %h %x %y"))
	for i in "${!region[@]}" 
	do
		region[i]=$(expr ${region[i]} "*" "2")
	done
	magick "$SCR_IMG/scr.tiff" -crop "${region[0]}x${region[1]}+${region[2]}+${region[3]}" "$SCR_IMG/scr.tiff" 

	tesseract "$SCR_IMG/scr.tiff" "$SCR_IMG/scr" &> /dev/null || die "failed to extract text"
  wl-copy < "$SCR_IMG/scr.txt" || die "failed to copy text to clipboard"
  notify-send "Text extracted from image" "$(head -c 100 "$SCR_IMG/scr.txt")" || die "failed to send notification"
  exit

I'm using this script from HN* to select regions on the screen and copy their text, I took out the line with mogrify. It uses spectacle but it takes a moment before opening the UI, is it possible and would it be faster if Spectacle stayed open in the background? The slurp CLI starts instantly for me for selecting regions, I looked for command line screenshot tools to maybe use with it or has its own region support but didn't find any. Neither maim scrot and grim don't work on Plasma Wayland. I installed the ksnip flatpak but the option for rectangular regions doesn't show for me.

* The script:

  #!/bin/bash 
  # Dependencies: tesseract-ocr imagemagick 
  # on gnome: gnome-screenshot 
  # on kde: spectacle
  # on x11: xsel
  # on wayland: wl-clipboard

  die(){
    notify-send "$1"
    exit 1
  }
  cleanup(){
    [[ -n $1 ]] && rm -r "$1"
  }

  SCR_IMG=$(mktemp -d) || die "failed to take screenshot"

  # shellcheck disable=SC2064
  trap "cleanup '$SCR_IMG'" EXIT

  #notify-send "Select the area of the text" 
  if  which "spectacle" &> /dev/null
  then
    spectacle -n -b -r -o "$SCR_IMG/scr.png" || die "failed to take screenshot"
  else
    gnome-screenshot -a -f "$SCR_IMG/scr.png" || die "failed to take screenshot"
  fi

  # increase image quality with option -q from default 75 to 100
  mogrify -modulate 100,0 -resize 400% "$SCR_IMG/scr.png"  || die "failed to convert image"
  #should increase detection rate

  tesseract "$SCR_IMG/scr.png" "$SCR_IMG/scr" &> /dev/null || die "failed to extract text"
  if [ "$XDG_SESSION_TYPE" == "wayland" ]
  then 
    wl-copy < "$SCR_IMG/scr.txt" || die "failed to copy text to clipboard"
  else
    # xsel -b -i  < "$SCR_IMG/scr.txt" || die "failed to copy text to clipboard"
    xclip -selection clipboard -i < "$SCR_IMG/scr.txt" || die "failed to copy text to clipboard"  
  fi
  # Notify the user what was copied but truncate the text to 100 characters
  notify-send "Text extracted from image" "$(head -c 100 "$SCR_IMG/scr.txt")" || die "failed to send notification"
  exit  #!/bin/bash 
  # Dependencies: tesseract-ocr imagemagick 
  # on gnome: gnome-screenshot 
  # on kde: spectacle
  # on x11: xsel
  # on wayland: wl-clipboard

  die(){
    notify-send "$1"
    exit 1
  }
  cleanup(){
    [[ -n $1 ]] && rm -r "$1"
  }

  SCR_IMG=$(mktemp -d) || die "failed to take screenshot"

  # shellcheck disable=SC2064
  trap "cleanup '$SCR_IMG'" EXIT

  #notify-send "Select the area of the text" 
  if  which "spectacle" &> /dev/null
  then
    spectacle -n -b -r -o "$SCR_IMG/scr.png" || die "failed to take screenshot"
  else
    gnome-screenshot -a -f "$SCR_IMG/scr.png" || die "failed to take screenshot"
  fi

  # increase image quality with option -q from default 75 to 100
  mogrify -modulate 100,0 -resize 400% "$SCR_IMG/scr.png"  || die "failed to convert image"
  #should increase detection rate

  tesseract "$SCR_IMG/scr.png" "$SCR_IMG/scr" &> /dev/null || die "failed to extract text"
  if [ "$XDG_SESSION_TYPE" == "wayland" ]
  then 
    wl-copy < "$SCR_IMG/scr.txt" || die "failed to copy text to clipboard"
  else
    # xsel -b -i  < "$SCR_IMG/scr.txt" || die "failed to copy text to clipboard"
    xclip -selection clipboard -i < "$SCR_IMG/scr.txt" || die "failed to copy text to clipboard"  
  fi
  # Notify the user what was copied but truncate the text to 100 characters
  notify-send "Text extracted from image" "$(head -c 100 "$SCR_IMG/scr.txt")" || die "failed to send notification"
  exit