If you are a cheapskate, and want to host WordPress yourself, on a Raspberry Pi sitting on your bookshelf – then good for you (me?). What you might find, when installing WordPress on your own LAMP box, is that installing plugins/themes etc requires an FTP account – credentials WordPress asks you for. This isn’t ideal, as in my self-hosted case I don’t have a Linux ‘user’ specifically for my WordPress instance, and I can’t figure out the arcane magic required to set up a specific FTP user that also shares access with my /var/www/whatever.com directories, messing with groups and permissions and whatnot..
All of that out of the way – I had that problem. I tried a variety of complex methods to get the thing working, and I couldn’t find an elegant solution – until I noticed that the root directory for my Apache install’s webpages (/var/www) wasn’t owned by my web-server user (www-data on Debian 9). A quick “sudo chmod -R www-data:www-data /var/www” and hey-presto, no more asking for FTP details – WordPress just works.