#####[Adding Ubuntu Repositories to the PsychOS 3.x series]#####

Ubuntu repositories can be adding to the PsychOS 3.x series by running
'sudo add-apt-repository ppa:some/ppa' like you normally would in a
terminal or by using the Synaptic Package Manager's 
"Settings --> Repositories" option. However, after adding the 
repository, followed by 'sudo apt update' or equivalent, you will get a
GPG key error. This can be fixed using the "MX Fix GPG keys" item from
the programs menu, or at least in most cases. You then run
'sudo apt update' again. But remember, do not pick newer than "Focal,"
aim for "Bionic" if you can, and do not bother going lower than 
"Trusty." Also, be very careful if doing this and try to only add Ubuntu
PPA repositories that target specific programs so as not to mess with 
any general updates.