You have a .hex file and a hunch something is off. Before you wire up a programmer or a debugger, you want to know what is actually inside it: where the address ranges sit, whether the checksums hold, whether two records quietly overlap. Hexmarrow: Firmware Lab is a place to ask those questions offline, without turning a first look into a whole toolchain project.
Open an Intel HEX artifact and it lays out the records, checksums, decoded addresses, memory map, and any overlaps or gaps. You can trace how the ranges fit together and note what looks wrong before you commit to hardware. It also inspects S-record, UF2, and ELF, keeps firmware notes in plain text, and ships a sensor-node.hex sample so you can learn the layout on something known before you point it at your own build.
Work on a copy, not your only good file. Read the checksums and address ranges before you conclude anything, then check the output against your established tools. Leave signing, release, and hardware calls for a separate, verified pass. The publisher's privacy page says the app is built around local inspection and collects no data.
The live App Store listing, price, version, availability, and capabilities still need a recheck by the deterministic publisher before this goes out.