It turns out that the solution is right here in our own backyard
and requires only 3 lines in /etc/vsftpd.conf
write_enable=YES
local_enable=YES
anonymous_enable=NO
That will allow username/password logins but not anonymous logins , and will allow you to write on the host filesystem ( eg do an upload).
Thank you @abhishek for cutting through all the unnecessary sophistication.
Now I understand what I am doing.
There is another more extensive ftp article here
It deals with active and passive ftp and how to handle firewalls.
I now have vsftpd running in all my Linux installations, except Void. In Void there is still available the original ftpd daemon. It comes packaged with the original ftp in a package called inetutils-ftp. It requires no configuration file at all. I guess that is the ultimate minimum config. I will continue to use original ftpd in Void.