Type: Line blending
Setup required: Custom timings programmed on the unit with remote or the units front buttons
Cost and availability: Very high cost to benefit, scarcely sold second-hand online. 
The DVDO iScan HD+ is one of the few (or maybe only) DVDO models to output 240p with a custom resolution. It outputs a 240p image that is a bit sharper than the Corio2 tvONE 750 which is also a line-blending scaler. With HDMI input via DVI, RGBs output via VGA and only 0.5 frames of lag, this should be a straightforward downscaler…
Unfortunately, it has no 480i output, grossly overscans a 720p input, and is very picky with sources. It can’t be faulted for not displaying HDCP protected content (the same as the OSSC Pro), but I cannot confidently say this will be a reliable downscaler, though your mileage may vary. With only 1 semi-reliable downscaling scenario of 480p>240p, only 1 customisable 240p resolution, and unpredictability with input sources, the DVDO iScan HD+ is a hard pass. Read through the following shmups thread for recommended 240p timings: https://shmups.system11.org/viewtopic.php?t=53807
Verdict: Not Recommended