Nothing CMF Phone 1 (tetris) for eOS-a15 3.1
e-3.1-a15-20250803-UNOFFICIAL-tetris.zip
https://sourceforge.net/projects/eosbuildsronnz98/files/OtherSmartphones/e-3.1-a15-20250803-UNOFFICIAL-tetris.zip/download
Please see sources and install instructions including recovery here:
https://xdaforums.com/t/rom-15-tetris-droidx-ui-official-stable-aosp.4749787/
Use it at your own risk!