With greetings from Fabby, I was referred to the elementary forums for this issue I am having with Geary.
Since Geary version 34.3, it should make use of Gnome Contacts list. However, it doesn't show me any suggestions either from the contact list or from the history of used mail addresses.
I am using Manjaro Gnome Stable. Geary is 3.34.2 (tags/3.34.2-0-g5b5d6d94) Gnome Contacts, version 3.34.1
Any help is appreciated.