Google has warned IMAP users of Gmail that "Less secure apps" access will be disabled after May 30. The following link explains that apps that are not "Less secure" use Oauth2: https://superuser.com/a/1708278/767015
The Google warning message says that Outlook 2019 should have access that is not "Less secure". I have Outlook 2019, but the dropdown list of encryptions has only SSL and TLS -- not Oauth2.
The aforementioned link explains that for Outlook 2013, Oauth2 can be enabled via a registry edit: (i) Go to HKCU:\Software\Microsoft\Office\15.0\Common\Identity, and (ii) Create a DWORD "EnableADAL" with value 1. I tried this on Outlook 2019, but still no Oauth2. However, I had a registry folder "16.0" instead of "15.0" as shown above, and that is the registry path I used.
I also tried the registry edit (with "15.0") on another machine with Outlook 2013, and still no Oauth2.
How can I enable Oauth2 on Outlook 2019? Google claims can 2019 supports the required encryption. What about Outlook 2013?