Is there a to enable "Allow less secure apps" for domain users using Google Apps Script? I browsed the G Suite Admin SDK reference but couldn't find anything. There's ResolvedAppAccessSettings: ListTrustedApps in Directory API > Security, but it's not what I wanted.
Thanks.
Unfortunately there is none. You can check this FAQ Allow or disallow less secure apps to access accounts and there is no mention of programatically way of doing this.
However, you may try to check the workaround in this google forum if it works for you.