I can reproduce
the fail of wget latest FP5 official a15
:\~$ wget https://images.ecloud.global/official/FP5/IMG-e-latest-a15-official-FP5.zip
--2025-10-18 07:45:58-- https://images.ecloud.global/official/FP5/IMG-e-latest-a15-official-FP5.zip
Resolving images.ecloud.global (images.ecloud.global)... 159.69.59.214, 2a01:4f8:231:b65::2
Connecting to images.ecloud.global (images.ecloud.global)|159.69.59.214|:443... connected.
HTTP request sent, awaiting response... 404 Not Found
2025-10-18 07:45:58 ERROR 404: Not Found.
The install page for FP5 seems to indicate [1] that a15is available but latest official is a14, so
wget https://images.ecloud.global/official/FP5/IMG-e-3.1.4-a14-20250915526529-official-FP5.zip
does proceed but
eosinstaller seems to be in error specifying Android 15 when this is not on the server while the official build is Android 14.
Report an issue or a report in Feedback for v3.1.4 are options.
I suggest better to revert to the regular install page Install /e/OS on a Fairphone FP5 - “FP5” where the user is in control of the process. The install happens with a script so is not so hard for fp5.
[1] Another error, a15 shown in image, a14 is available.
