I've just started using the FLX1s (after a week of fiddling around trying to get WhatsApp conversations transferred) and went to call someone from my contacts list. What I've found is that I can open the phone app then select someone from the Contacts to call, but not open Contacts app and call someone from it.
Conversely Chats doesn't offer to Chat with someone from the Contacts list. If I want to text someone, I have to memorize their phone number then enter it in Chats. Once there, it seems to pick up the person texted from the Contacts list so their name is displayed.
These are not deal-breakers for me, but the phone would be a lot easier to use if Chats worked like the Phone app and let you select a destination from Contacts. And Contacts would be a lot more useful it offered the option to call or text a number.
Interesting. I checked it and you are right you cant call from the "contacts app" but you call send e-mails and open websites from there.
It seems like the flathub contacts ever had the ability to call from there.
https://discourse.gnome.org/t/gnome-contacts-call-and-text-from-contact/18323
These are upstream issues. Not that it would be cool to have everything working seamlessly :D.
Because of this and some other things I started while a go my Phofono project which will solve all this problems (I actually tried to do the stuff for Calls, Chatty and Contacts first but it was way too complicated for my brains).
Use at your own risk and do not trust some stranger from internet. Some stuff is kind of hacky but it works for me and I test these things with high intense every day.
https://gitlab.com/Alaraajavamma/phofono
You can also ask if needed
