Is it then a lack of national priority, funding constraints, or technical know-how that is causing it to be so far out? In almost every other facet military or economic China has concrete plans of producing a prototype/test article/etc
Only things I haven’t noticed obvious progress of (or much optimism of seeing it soon) are stealth bombers or modern subs (type 96, type 95, etc).
As for the Raider you’re right the first flight is expected in 2021, likely to be pushed into 2022.
"Concrete plans" -- we never have any truly "concrete plans" for any new big ticket PLA military project.
Look back on other big ticket air, naval, missile and ground projects in recent times. We never had any sort of official timetable for when certain milestones might be achieved.
J-20, SAC Flankers, Y-20, 052D, 055, DF-17, DF-41, ZTQ-15, QBZ-191, whatever -- before any of them officially "emerged" we never had any sort of public schedule or "concrete plan" for when they would be in service from the govt or the military.
As for H-20 specifically, it all depends on when the first aircraft flies.
Stealth bombers are complex aircraft, and the original B-2 first flew in 1989 and entered service in 1997 --- that's 8 years later.
Now, I'm not saying H-20 will necessarily take 8 years between maiden flight and entry into service, but I am saying that you need time for a new aircraft to be tested and developed before production and entry into service, and it isn't something you can simply accelerate by throwing more money or engineers at the problem.
For an aircraft as complex as H-20, I would expect at least 5 years in this day and age, and I wouldn't be surprised if it was more.
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I think this is bold also. What has changed for things to be up in the air right now. What evidence is there that there have been setbacks or changes in priorities etc. or something to cause things to be ‘up in the air’?
Basically, the one thing we are waiting for which is yet to be determined is when H-20 will make its maiden flight.
Once H-20 makes its maiden flight we can start to make predictions for when it might enter service.
But right now, all we know is that the first H-20 is being built, but we don't know how far long it is. We don't know if it will fly in 2021, or 2022 or later.
A stealthy strategic bomber is a complex aircraft, and we don't know what their original specific aim for a maiden flight is/was, so we don't know if things are proceeding according to their schedule or not.
However it is certainly bold to assume that whatever current schedule they're operating on means we should expect H-20 to enter service in 2027. There is no reason for us to be able to confidently make such an assertion in good reasoning, at best it can be stated in with hopefulness.
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Edit: as for modern submarines (09V, 09VI) -- well yes, you're not going to see much progress of it until the first boat is literally launched. Nuclear submarines are among the most secretive military projects in the PLA, they keep very secretive about them, and their construction easy to hide.
What's going to happen is one day we're going to wake up and see on satellite that Bohai has launched a new submarine that seems different to previous submarines and we will have weeks and months to speculate which exact type it is before tentative confirmation that it's an 09V or 09VI.