If you have experience with software, learning embedded concepts isn't a huge leap. At least in my area, aerospace, defense, and automotive tend to be the biggest, easiest employers to get started with. They will hire basically anyone with a solid grasp of C, OSes, and basic computer architecture (at an undergrad level.)

I find embedded really rewarding. A 20 year old embedded-C code base generally follows the same design patterns and coding conventions and styles that you'd use today, and don't feel "old" or like they need to be rewritten. A 7 year old JS code base, on the other hand, is largely outdated, and may be written in a nearly extinct framework by the time it is your turn to maintain it. If you get tired of giving up time on the weekends so you can learn a new framework, consider hopping over!