Ask HN: Good resources to brush up on firmware reversing?

Did some software reversing a couple of decades ago, had a SoftICE license, hot-patched running code in production, etc. That is, I know the basics, but the specifics are outdated.

I am now trying to understand if it's at all possible to reverse a firmware for a specific (sport activity) watch, because it is really annoying in some places and I'd like to patch that.

Is anyone aware of good places to read on this subject? More specifically, making firmware dumps either directly from the device or from update packages, reversing the update mechanism, etc. Trying to find other people's work in this area. TIA!