Add me to the list too... Just got a "new" (refurbished) Pixel 6 Pro on Amazon.
I just got the phone and had no issues with the stock OS. I played with the stock for about a half an hour on and off to make sure everything worked and so I could see what the stock OS was like compared to Graphene (I'm an iPhone user trying to switch). The phone had no issue maintaining wifi over this time (a total of several hours - but again, I only used it for a total of about a half hour, if that). Everything was working fine. I then installed GrapheneOS without issue - the brand new version that just came out yesterday. I literally did nothing with the OS besides change the wallpaper, install F-Droid and Aurora Store. No other apps whatsoever. After this I left it for a few hours unattended, came back, no wifi connection. Didn't change anything with my router settings, and all other devices in my house work fine. I did not monkey with any permissions / settings in the device. I simply cannot connect to my home network all of a sudden. I gave F-Droid / Aurora Store full permissions when installing - not that that should mean anything I don't think. Yes, I tried the mac address options for the network (per connection / per device / mac). It goes from "obtaining IP Address" to "Disconnected" (and I think I've also seen "failed to obtain IP Address") regardless of which of those settings I try.
I've looked in my router and see nothing to be concerned about. I have under 50 DHCP leases, so its not like its bumping into an upper limit that I can see.
Assuming there is actually some sort of DHCP limit that I'm bumping up against even though I'm under 50 devices, I think that the first time someone connects to a wifi network on GrapheneOS, there should be a short explanation of those three options and why someone may not want to use the "randomizing" thing at home. If this is all it takes for issues with many home routers to pop up, then its worth mentioning before someone fills up their DHCP allowance. Just my newbie opinion of course.
Yes, I'm a networking idiot, but I do have 25 years or so PC tech / repair experience, so I should be able to figure this kind of thing out. The fact that I can't leads me to believe this is some sort of bug...