what is the structure/system denoted by structural/systematic?
In the OP definitions, 'systemic' covers 'embedded in the normal practices of society or an organisation'. So that could be, for example, the housing market.
Or the educational system, school policies, teacher quality, and associated opportunities.
I would pose that the majority of structural racism arises as a result of legacy factors, both in the form of networking opportunities for the privileged, and educational/policing redlines.
I would not want to raise a child in my current school district, where all the budget goes towards metal detectors and security instead of theaters and classrooms and teachers.
And beyond that, simply the fact that minorities have so much less economic momentum per capita is itself "systemic".
But whenever you propose methods to equalize economic momentum within society, or to equalize educational opportunities, the racists flip their shit.
But these aren't racism. The schools are a reflection of the students they get. They aren't spending all that money on security to punish blacks, they're spending it because they need to. There's also the issue that putting expensive stuff in such a school is just throwing money away--it's just going to end up broken or stolen in short order. This is a community problem and can only be fixed by fixing the community issues. That's very hard, though, it's much easier to scream "discrimination!"