Older versions of the FP Open OS note by me: implicit: not FPOS (note that the Open OS does not include any Google-applications and services), you get a (typically) include an older version of TWRP already, which might be sufficient. See below on how to use this older TWRP version to install a newer version (if desired). Since OS version 19.11.2 (december 2019), a stock android recovery is included instead.