OK, so I reverted back to Android and tried again for CE 21.0 (USB burning tool not working even with newest 3.2, not recognizing the box luckily Amlogic_Burn_Card_Maker_v2.0.2 saved my day).
The result was the same, stuck at boot logo with artifacts. Like @MilePule mentioned if I plug in the wired cable the box did connect to the router with an IP, but since it was during first boot ssh was not enabled so I cannot see what is going on.
I took the liberty and switched the dtb back to the one used on CE 20.1 and vola!! It worked!! Boot normally and I even installed 21.0 on emmc!
FYR, the dtb I’m using is with this MD5 included in 20.1:
s4_s905w2_2g.dtb- 1b248203bf8b9b53cc0a7a7623c39173
Another issue is connecting to a WPA2/WPA3 mixed wireless AP is impossible, system reports “No Input/output error”, no idea if it is realted but to me it feels something like the one mentioned here
But another old S905 (no postfix, just S905) box with CE9.2.8 can connect to the same AP without any issue!
If change encryption to WPA2 only then CE can connect to the AP fine.