'net usershare' returned error 255 when creating a share

This looks like a nautilus-share issue.

Have you fully ensured that samba is installed?

sudo apt install samba smbclient

Ensure the directory placement:

sudo mkdir -p /var/lib/samba/usershares/

sudo chmod go+rwx /var/lib/samba/usershares/

Set your usergroup:

sudo usermod -aG sambashare $USER