MintにNitroshareをインストールできない

Nitroshareアプリをインストールしようとしていますが、常に同じ問題が発生します

端末では、次のように言います。

alex@satellite:~$ sudo apt-add-repository ppa:george-edison55/nitroshare
Cannot add PPA: ''This PPA does not support focal''.

次の手順に従ってみました。これ

私は次のような結果を得ました。

alex@satellite:~$ sudo apt update
Ign:1 http://mint.ipacct.com/packages una InRelease
Hit:2 http://mint.ipacct.com/packages una Release                              
Hit:3 http://archive.ubuntu.com/ubuntu focal InRelease                         
Hit:4 http://archive.ubuntu.com/ubuntu focal-updates InRelease                 
Hit:5 http://security.ubuntu.com/ubuntu focal-security InRelease               
Hit:6 http://archive.ubuntu.com/ubuntu focal-backports InRelease    
Hit:8 http://archive.canonical.com/ubuntu focal InRelease
Reading package lists... Done
Building dependency tree       
Reading state information... Done
All packages are up to date.
alex@satellite:~$ sudo apt install --reinstall ca-certificates
Reading package lists... Done
Building dependency tree       
Reading state information... Done
0 upgraded, 0 newly installed, 1 reinstalled, 0 to remove and 0 not upgraded.
Need to get 145 kB of archives.
After this operation, 0 B of additional disk space will be used.
Get:1 http://archive.ubuntu.com/ubuntu focal-updates/main amd64 ca-certificates all 20210119~20.04.2 [145 kB]
Fetched 145 kB in 0s (413 kB/s)           
Preconfiguring packages ...
(Reading database ... 318898 files and directories currently installed.)
Preparing to unpack .../ca-certificates_20210119~20.04.2_all.deb ...
Unpacking ca-certificates (20210119~20.04.2) over (20210119~20.04.2) ...
Setting up ca-certificates (20210119~20.04.2) ...
Updating certificates in /etc/ssl/certs...
0 added, 0 removed; done.
Processing triggers for ca-certificates (20210119~20.04.2) ...
Updating certificates in /etc/ssl/certs...
0 added, 0 removed; done.
Running hooks in /etc/ca-certificates/update.d...

done.
done.
Processing triggers for man-db (2.9.1-1) ...
alex@satellite:~$ sudo apt-add-repository ppa:george-edison55/nitroshare
Cannot add PPA: ''This PPA does not support focal''.

私は上記のようにしようとしました。場所

これは私のシステムです。

alex@satellite:~$ neofetch
             ...-:::::-...                 alex@satellite 
          .-MMMMMMMMMMMMMMM-.              -------------- 
      .-MMMM`..-:::::::-..`MMMM-.          OS: Linux Mint 20.3 x86_64 
    .:MMMM.:MMMMMMMMMMMMMMM:.MMMM:.        Host: SATELLITE C660 PSC1QE-01D006N5 
   -MMM-M---MMMMMMMMMMMMMMMMMMM.MMM-       Kernel: 5.4.0-94-generic 
 `:MMM:MM`  :MMMM:....::-...-MMMM:MMM:`    Uptime: 1 hour, 18 mins 
 :MMM:MMM`  :MM:`  ``    ``  `:MMM:MMM:    Packages: 2154 (dpkg), 11 (flatpak) 
.MMM.MMMM`  :MM.  -MM.  .MM-  `MMMM.MMM.   Shell: bash 5.0.17 
:MMM:MMMM`  :MM.  -MM-  .MM:  `MMMM-MMM:   Resolution: 1366x768 
:MMM:MMMM`  :MM.  -MM-  .MM:  `MMMM:MMM:   DE: Xfce 
:MMM:MMMM`  :MM.  -MM-  .MM:  `MMMM-MMM:   WM: Xfwm4 
.MMM.MMMM`  :MM:--:MM:--:MM:  `MMMM.MMM.   WM Theme: Mint-Y-Aqua 
 :MMM:MMM-  `-MMMMMMMMMMMM-`  -MMM-MMM:    Theme: Mint-X-Aqua [GTK2/3] 
  :MMM:MMM:`                `:MMM:MMM:     Icons: Mint-Y-Aqua [GTK2/3] 
   .MMM.MMMM:--------------:MMMM.MMM.      Terminal: xfce4-terminal 
     '-MMMM.-MMMMMMMMMMMMMMM-.MMMM-'       Terminal Font: Monospace 12 
       '.-MMMM``--:::::--``MMMM-.'         CPU: Intel Pentium B980 (2) @ 2.400G 
            '-MMMMMMMMMMMMM-'              GPU: NVIDIA GeForce 315M 
               ``-:::::-``                 Memory: 1055MiB / 3909MiB