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Also Dells are not standard ATX, the cases and motherboards are backwards.
They mostly are fully compliant with the usual standards now and have been for ages.
OP, how old is the PC? Some of the older Dell motherboards won't take a 460, 470 and so on as they require UEFI (but likely will take a 1050, 1060 etc).
2nd gen i5 so 5 years old
2nd gen i5 so 5 years old
yeah
I can conclude the machine did not boot with a RX460
what are the alternatives around £100