Maybe the best part of the FP5 that is talked about little is that the main SoC is not a consumer grade Qualcomm chip, but an industrial grade one that will get driver and firmware upgrades for a much longer time than the consumer ones.
In addition it is fairly similar to other slightly older Qualcomm chips that already have main-line Linux kernel support, so the prospects of running Mobian or PostmarketOS on it are quite good.