I scrolled through https://github.com/dbohdan/embedded-scripting-languages

And there are some options. You could achieve barebones VM protections with Pawn(the language enforces very little otherwise, though). You could use something ref-counted like a TCL implementation, which would allow you to design around linear allocation times. The vast majority are using some kind of tracing collector of course, but I wouldn't say this is a total loss for achieving a combination of real time and memory protection.