rost@DEBIAN999:~$ sudo apt-get install gnuplot
Reading package lists... Done
Building dependency tree      
Reading state information... Done
The following NEW packages will be installed:
  gnuplot
0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
22 not fully installed or removed.
Need to get 0 B/128 kB of archives.
After this operation, 139 kB of additional disk space will be used.
Selecting previously unselected package gnuplot.
(Reading database ... 146935 files and directories currently installed.)
Preparing to unpack .../gnuplot_5.2.6+dfsg1-1+deb10u1_all.deb ...
Unpacking gnuplot (5.2.6+dfsg1-1+deb10u1) ...
Setting up llvm-7-runtime (1:7.0.1-8+deb10u2) ...
Setting up llvm-7 (1:7.0.1-8+deb10u2) ...
Setting up llvm-6.0 (1:6.0.1-10) ...
Setting up lib32gcc1 (1:8.3.0-6) ...
Setting up libgcc-s1:amd64 (10.2.1-3) ...
Setting up libomp-7-dev (1:7.0.1-8+deb10u2) ...
Setting up lib32stdc++6 (8.3.0-6) ...
Setting up libclang-common-7-dev (1:7.0.1-8+deb10u2) ...
Setting up libc6-dev:amd64 (2.28-10) ...
Setting up gnuplot (5.2.6+dfsg1-1+deb10u1) ...
Setting up pepperflashplugin-nonfree (1.8.7) ...
--2021-01-05 19:52:09--  https://get.adobe.com/flashplayer/webservices/json/?platform...
Resolving get.adobe.com (get.adobe.com)... 193.104.215.66
Connecting to get.adobe.com (get.adobe.com)|193.104.215.66|:443... connected.
HTTP request sent, awaiting response... 302 Found
Location: https://www.adobe.com/products/flashplayer/end-of-life.html?... [following]
--2021-01-05 19:52:10--  https://www.adobe.com/products/flashplayer/end-of-life.html?...
Resolving www.adobe.com (www.adobe.com)... 87.245.216.82, 87.245.216.121, 2a02:26f0:4800::215:5963, ...
Connecting to www.adobe.com (www.adobe.com)|87.245.216.82|:443... connected.
HTTP request sent, awaiting response... Read error (Success.) in headers.
Retrying.

--2021-01-05 19:52:26--  (try: 2)  https://www.adobe.com/products/flashplayer/end-of-life.html?...
Connecting to www.adobe.com (www.adobe.com)|87.245.216.82|:443... connected.
HTTP request sent, awaiting response... Read error (Success.) in headers.
Retrying.

--2021-01-05 19:52:43--  (try: 3)  https://www.adobe.com/products/flashplayer/end-of-life.html?...
Connecting to www.adobe.com (www.adobe.com)|87.245.216.82|:443... connected.
HTTP request sent, awaiting response... Read error (Success.) in headers.
Giving up.

ERROR: failed to determine upstream version
More information might be available at:
  http://wiki.debian.org/PepperFlashPlayer
Setting up libomp-dev (1:7.0-47) ...
Setting up libtsan0:amd64 (8.3.0-6) ...
Setting up libncurses-dev:amd64 (6.1+20181013-2+deb10u2) ...
Setting up libclang-common-6.0-dev (1:6.0.1-10) ...
Setting up llvm-6.0-dev (1:6.0.1-10) ...
Setting up libgcc-8-dev:amd64 (8.3.0-6) ...
Setting up libstdc++-8-dev:amd64 (8.3.0-6) ...
Setting up libtinfo-dev:amd64 (6.1+20181013-2+deb10u2) ...
Setting up llvm-7-dev (1:7.0.1-8+deb10u2) ...
Setting up libobjc-8-dev:amd64 (8.3.0-6) ...
Setting up clang-6.0 (1:6.0.1-10) ...
Setting up clang-7 (1:7.0.1-8+deb10u2) ...
Processing triggers for man-db (2.8.5-2) ...
Processing triggers for systemd (241-7~deb10u5) ...
Processing triggers for libc-bin (2.28-10) ...
rost@DEBIAN999:~$ gnuplot

    G N U P L O T
    Version 5.2 patchlevel 6    last modified 2019-01-01

    Copyright (C) 1986-1993, 1998, 2004, 2007-2018
    Thomas Williams, Colin Kelley and many others

    gnuplot home:     http://www.gnuplot.info
    faq, bugs, etc:   type "help FAQ"
    immediate help:   type "help"  (plot window: hit 'h')

Terminal type is now 'qt'
gnuplot> plot sin(x)
gnuplot>

РАБОТАЕТ!!!!

Обратите внимание на попытку выкачать флеш с сайта adobe
--2021-01-05 19:52:43--  (try: 3)  https://www.adobe.com/products/flashplayer/end-of-life.html?...
Connecting to www.adobe.com (www.adobe.com)|87.245.216.82|:443... connected.
HTTP request sent, awaiting response... Read error (Success.) in headers.
Giving up.

Поддержка кончилась, флеша больше не будет.