My printer needs HP plugin for HPLIP. In openSUSE Leap 15.3 I have installed
HPLIP 3.20.11.
When I try to print, GUI dialog appeared to install missing plugin. I went
throw wizard and selected to download it. But when I try to download/install
it, I get the following error:

.hplip/hplip-3.20.11-plugin.run file does not match its checksum. File may have
been corrupted or altered

Later I manually managed to download it from 
https://developers.hp.com/sites/default/files/hplip-3.20.11-plugin.run 

Executing it failed:

> sudo sh hplip-3.20.11-plugin.run 
Verifying archive integrity... All good.
Uncompressing HPLIP 3.20.11 Plugin Self Extracting
Archive..............................................................
Error importing HPLIP modules.  Is HPLIP installed?

Only later I found this error because of python2 usage instead of python3 for
execution of plugin_install.py via hplip-plugin-install.


Thus workaround was:
wget https://developers.hp.com/sites/default/files/hplip-3.20.11-plugin.run
sh ./hplip-3.20.11-plugin.run --nox11 --target mydir
cd mydir
sudo python3 ./plugin_install.py -i