I just came across this on Twitter. Vanilla chrome does not delete Google cookies when cookies are deleted. Is ungoogled-chromium affected by this?

This seems to be related to the "Sign-in to Chromium" function of the browser which is disabled.
Otherwise all Google cookies are deleted, at least the ones contained in the 'Cookies' file found in the browser profile.
If this is really the case, this issue can be closed. Is there a way to check this?
You can run Chromium with a new temporary profile, login to various Google sites,
rm -rf /tmp/chromium-profile && chromium --user-data-dir=/tmp/chromium-profile
and inspect the cookie database with e.g. sqlitebrowser:
sqlitebrowser /tmp/chromium-profile/Default/Cookies
I think I will give this a try tomorrow. Thanks.
Trying the method from @xsmile, I can confirm that deleting cookies actually deletes all cookies on ungoogled-chromium-69.