Yaiy, finally, could get an #OpenWrt initramfs to boot on this #rtl93xx based switch, a #XikeStor SKS8310-8X! The OpenWrt commit message warned that you need to use a "suitable SFP module (some work, some don't)".
And I tried a bunch... (3m DAC: Cisco SFP-H10GB-CU3M, Flexoptic 10/100/1000BASE-T / RJ45 T.C12.02.A). Now a Ubiquiti OM-SM-10G-D worked.
And probably also only after updating a BPI-R4 I connect with from stock fw to 24.10.5 (SFP hotplugging seemed flaky before that?)

Interesting, the #XikeStor / #Seekswan SKS8300-12X switch seems to be rtl93xx based, too, with the most SFP ports I've seen for a #Realtek #rtl93xx or #rtl83xx device. According to this page it should be #rtl9313: http://visit.seekswan.com:6555/xksupport/SKS8300-12X.htm
And maybe it wouldn't be too hard to add to #OpenWrt as the smaller XikeStor SKS8300-8X is already supported there: https://openwrt.org/toh/hwdata/xikestor/xikestor_sks8300-8x

Xユーザーのxikestorさん: 「Attention SKS3200 series switch users! We do have a reset button!🤣 #xikestor #networkswitch https://t.co/Ch5NpNDoBX」 / X https://x.com/XikeStor0963/status/1868836356518297773

#八丁 （ #Xikestor ）の激安SFPスイッチ、L3の #SKS8300-8X については後継機としてSKS8310-8Xが出ている模様。4ポートごとに分かれてファン付きになるらしい。併売については不明。L2もあるし、多分中身同じ他ブランドもあるしで、すぐに困ることはないと思うけれど。