I installed UBPorts Ubuntu Touch on my mobile on 2021-06-11.
(love Ubuntu Touch in its own right - and have had a huge sense of relief ever since)
I installed and configured Dekko 2 for a firstname.lastname@example.org - the only reference in the mobile to my gmail account - and I have been receiving emails just fine and didn't receive any security notifications from Google (though I only connect to the Internet very seldomly).
Yesterday, I connected the smartphone to a Wi-Fi, Decko downloaded my new emails immediately and I received 2 security emails (in the same minute) from Google warning me that «someone had used my password to login into my account and Google blocked the login»
(^ translated from the language I received it in).
Why would Dekko have triggered such a block/warning from Google?
I usually severely distrust such security warnings from the likes of Microsoft email servers, since they appear to have a strong tendency to «judge» any non-Microsoft clients as untrustworthy and worthy of being «security» blocked (with "security" probably meaning the security of MS' revenue).
However, I have used the smartphone to access my emails some 10(?) times already, without ever triggering any such warnings. Further, the Dekko client did get to download the emails, including the security warning emails themselves.