Just to pre-emptive the comments about how it's silly to use Google services on GrapheneOS, I get it. That being said, I can't get a few things to work properly. I have a Google Pixel 6a.
When using Google Assistant, it always pulls up with the message, "Sorry, I can't send messages with Google Chat" every time I say the command, "Text (name of contact)". It has no issues texting a specific number with SMS if I say "text (1234567890)". It does the same thing with calling. Sometimes, it allows me to choose from similar contacts in my Google account, random e-mail addresses and the like. One thing to note, is it will not let me save a custom person in my Google assistant settings (mother, brother, etc.) although I don't want to do that in the first place.
Another thing is, the function to wake Google Assistant with a voice command ("Ok, Google") has the option greyed out, "this feature is currently unavailable to your device". Seems weird.
The other thing with Google Files is I can't set it as a default for opening files from the internet. The native GrapheneOS Files app doesn't have the ability to extract .zip files. Google Files does. This issue is minor, but, I thought I would make note of it incase anyone has it figured out.
Anyone have any ideas? I've been fighting with these problems for days now. I can't find any helpful information anywhere. support.google had a thread that had a similar problem, but the moderators locked it after linking to some useless canned response.