Strictly bounded anything (hard real-time) is an entirely different category, with very few uses for the average person - and contrary to what one might think from its name, it is not “fast” at all. It’s mostly about “calculating the trajectory of that incoming projectile should definitely happen in 0.3s”, which is many orders of magnitude more than what a modern computer would take to do 3 multiplications.
But to answer your question, there is JamaicaVM and many niche JVM implementations with hard real time GCs — but it’s simply false that a GC would be somehow a problem for most of your devices.
Hard real-time has a huge amount of uses for the average person. I just made toast -- the software-controlled thermostat in my toaster oven has (slow) hard bounds on its sense-to-control latency to avoid dangerous overheating. Before that, I brushed my teeth -- the brushed motor controller detects a motor stall by increased current if I brush too hard and stall it, shuts down the motor to avoid overheating (with a hard real-time sense-to-actuate constraint), and beeps to inform me. Then I spent some time on HN, with a laptop with PMICs and other microcontrollers that have hard real-time constraints all over the place. By far the majority of my computer interactions so far today have been with computers that have hard real-time constraints, and I haven't even gotten in my car yet!
But to answer your question, there is JamaicaVM and many niche JVM implementations with hard real time GCs — but it’s simply false that a GC would be somehow a problem for most of your devices.