When you get a new device you should test every function and especially the modem and the WiFi/BT, for example LineageOS emphasises this in the instructions, you have to be sure that the phone was already in a working condition before deGoogling.
It’s feasible both with fastboot and the SPFlash tool, How to Manually Install or Update the OS on Your Brax Device - Open Source Community Guide
For SPFlash the appropriate file is the *spflash.zip (brax3/iode-7.2-20260131-brax3-spflash.zip · master · ota / release · GitLab), inside that there is an XML file in the download_agent folder that is loaded to the tool describing the partitions. The *spflash.zip contains all the appropriate partitions as .img files, maybe the recovery has to be flashed separately but you will see that in the instructions.
Two topics, iodeOS download , How to Manually Install or Update the OS on Your Brax Device