Looking at the FAQ provides more details on various ways GrapheneOS phones home by default. Thankfully, some of these "services" can be disabled.
The time service is enabled by default but can be disabled.
"An HTTPS connection is made to https://time.grapheneos.org/ to update the time from the date header field."
"Network time can be disabled with the toggle at Settings System Date & time Use network-provided time."
Connectivity checks are enabled by default but can be disabled.
"Connectivity checks designed to mimic a web browser user agent are performed by using HTTP and HTTPS to fetch standard URLs generating an HTTP 204 status code."
"You can change the connectivity check URLs via the Settings Network & internet Advanced Internet connectivity check setting. At the moment, it can be toggled between the GrapheneOS servers (default), the standard Google servers used by billions of other Android devices or disabled."
Why these are enabled by default, i.e., opt-out instead of opt-in, is strange considering this OS is aimed at technical, security and privacy-conscious users. Users who would surely know what services they want and be capable of enabling them.
The time service is enabled by default but can be disabled.
"An HTTPS connection is made to https://time.grapheneos.org/ to update the time from the date header field."
"Network time can be disabled with the toggle at Settings System Date & time Use network-provided time."
Connectivity checks are enabled by default but can be disabled.
"Connectivity checks designed to mimic a web browser user agent are performed by using HTTP and HTTPS to fetch standard URLs generating an HTTP 204 status code."
"You can change the connectivity check URLs via the Settings Network & internet Advanced Internet connectivity check setting. At the moment, it can be toggled between the GrapheneOS servers (default), the standard Google servers used by billions of other Android devices or disabled."
Why these are enabled by default, i.e., opt-out instead of opt-in, is strange considering this OS is aimed at technical, security and privacy-conscious users. Users who would surely know what services they want and be capable of enabling them.