Was recently checking on rtl9303 support as I saw some even cheaper options on aliexpress and wanted an 8 port SFP+ 10gb switch for fibre distribution.
The PR looks like it stalled too. Plus at least for me this switch is more expensive than the Onti (which I hope is realtek =P, but there's some other sellers too) I'm looking at on aliexpress. But I guess the unmanaged version is in between.
Perhaps ask in what seems to be the defacto realtek support thread? Support for RTL838x based managed switches
Also check out as per U-Boot for XGS12xx switches (and others based on realtek rtl930x) regarding u boot options? Was mentioned by olliver ages ago? Hasivo switches - #33 by olliver