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That bike24 description says 'not for ST levers'
They're obliged to conform to a strict interpretation of the Shimano compatibility chart. In practice, they're fine if properly adjusted. I think the shorter total lever throw of STIs (because the gear lever hits the bars) means that if you set up the initial pad clearance at the maximum permitted, you might run out of lever travel before generating enough stopping power to pass the deceleration test.
TRP are fine but needlessly expensive next to the Shimano ones. Tektro 926 is functional but a substantial drop in quality of design and execution.
German shops are usually a good bet for Shimano non-series and touring parts, Bike24 have black 353s in stock https://www.bike24.com/p2168610.html
It's worth getting the XT shoes https://www.bike24.com/p223508.html while you're at it as the moulded-t0-the-bolt pads are the main thing which makes the Sora worse than the Tiagra/105 level brakes.