Are there templates for printable labels such as Avery?
Yes, I can’t answer completely as I don’t use them. On the upper left of writer File/New/Labels/Brand/AveryA4 etc. also from Termplate center many more to install. https://extensions.libreoffice.org/templates
Also from Format /Page default is letter, but you can chose a3, a4, a5, a6 etc. And I’ll bet their our more I don’t know. You can also create your own.