Here are the steps I used to run the jitouch v2.74 on Big Sur

1. Install jitouch normally, and give access to it in "accessibility" (in pref panes / security and privacy - tick the box in front of jitouch).

2. Copy - paste the script above in this thread in a text editor, and save it somewhere on your drive where it will stay there for a while. Lets name it jitouch.sh here. The script above is written to work if jitouch has been installed only for current user. if you install it for all users, please see my note below.

3. Open a terminal, then go to the folder where your script is stored using the cd command (for example if your script is on the desktop, enter "cd ~/Desktop", without the brackets) and then do:
chmod +x jitouch.sh
This will make your script executable

4. still in the terminal, type:
bash jitouch.sh
You may have to give permission to your "terminal" and "launcher" in prefpanes / security and privacy (tick the boxes in front of terminal and launcher). If it is the case, run again the script until you see the jitouch icon popping up in the upper right of your screen.

5. Now, this fix only works after you run the script, and will be disabled at each startup. Of course, like me, you are lazy (or efficient) and you want to automatise it. You can do as explained here: https://stackoverflow.com/questions/6442364/running-script-upon-login-mac
On your first startup, you will have to grant accessibility permissions to your app in PrefPanes/security and privacy, the same way as we previously did. Jitouch icon should popup 5-10 seconds after you logged in.
Note that there are other options to do so, with launchd for exemple, but it's a little bit trickier if you are not used to it.

Some notes:
- If you are uncomfortable with using a terminal and don't know how to access the folder where your script is located, you can simply type "chmod +x " (with the space after the x) and then drag and drop your file on the terminal window. Doing as such will type down the complete access path to your script.
- If you installed jitouch for all users, change the script to remove the ~ at the beginning of the last line (the ~ means it is installed in your personal user's library).
- It may not work at the first attempt. I had to try 2-3 installs of jitouch and run the script 2-3 times before all the security and privacy options were rights. Once all the permissions have been granted, it should work!
- if you see errors while trying to save your automator script; close Automator and open a terminal and type:
xcode-select --install
then try to create the automator script again.