Here I would like to share my experience of using /e/OS on Fairphone 4 in Japan, where Fairphone series are not officially supported.
On the stock ROM, Fairphone 4 did not conduct IMS registration or recognize VoLTE networks of docomo and KDDI. It was unnerving, but it has been reported multiple times on the official Fairphone forum that after the stock OS on FP4 was updated to Android 12 the phone no longer recognized network connections in Japan, and I guess this might be the case.
I tried to establish network connections by editing APN configurations and resetting them without success, so I proceeded anyway to flash /e/OS despite lack of IMS registration and VoLTE provision.
After flashing /e/OS via EasyInstaller, though I needed to create an APN configuration for my MVNO as specified by it for KDDI, the phone was successfully provisioned for VoLTE It also recognizes 5G network as well, with working dual SIMs.
I tested some combinations, and here is what I got:
- physical SIM card of KDDI (4G): works
- physical SIM card of KDDI (5G): works
- eSIM of docomo (4G): works
- physical SIM card of docomo (5G): works
I have not tested connectivity of eSIM connection on KDDI. On Fairphone’s forum there is a report that eSIM of KDDI was not recognized on Fairphone 4, while /e/OS might recognize one. Connectivity of Softbank and Rakuten, the other two large mobile carriers, is not tested as well, but it might be worth for some tests.
After installation since several days I have not experienced a critical problem yet.
Here is the phone’s information:
Baseband version: MPSS.HI.2.5.1-01001-BITRA_GEN_PACK-1
Kernel version: 4.19.157-perf-g81c35c565a1b #1 Wed Jan 10 12:32:28 UTC 2024
Build number: e_FP4-user 12 SQ3A.220705.004 eng.root.20240110.121825 dev-keys
Hope this helps for those who would like to use Fairphone 4 in Japan.
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