This type of site is what always has me considering moving “up” in the stack. Remote work on either hardware or systems level programming (embedded) is almost non existent. Remote and not full-time is even rarer.
SaaS could be a good transition, there are quite a few SaaS shops using C++ for example. Or possibly backend if you're willing to do some cloud based side projects. Embedded is a lot of fun but IMHO there is more opportunity and compensation up the stack.
Which one?