I use Ubuntu 17.10 and recently received a warning from Google that:
Some apps & devices use less secure sign-in technology, which could make your account vulnerable. Google recommends turning off access to these apps.
So I clicked on the button to turn off access to these apps. I remember that Ubuntu was mentioned in the resulting process. The Google designated low risk apps (see below) I left with access were Gnome, Gnome Evolution and Thunderbird.
3 apps with low-risk access to your data It's safe to keep giving these apps or services access if you trust and use them. They have low-risk account access or Google verified their developers' information.
When I came to use Thunderbird it couldn't read the mails from my Googlemail account.
So I went back to the Google security page and switched the access to less secure apps back off. Now everything works again but Google keep telling me my account is less secure.
As the only software that needs access to my Google account the Gnome calendar and Thunderbird I would have thought that just allowing these access would be sufficient but it seems that Ubuntu also needs access. Does anybody know why and/or what I can do to allow access to just Thunderbird and Gnome which Google are happy are safe?