Probable you have compatibility issue with your very old motherboard. Some models of RX cards demand UEFI support by the motherboard.
Try to update BIOS You need another GPU to load your system and run this file under OS environment
Or at least try to reset BIOS (take out motherboard battery for 5 sec and return it back)
I had the same issue as I bought a used i5 system with the same board to set up my son with a system to play Overwatch with. When I plugged in the Asus rx 460 board, the same thing happened where it just stayed frozen on the BIOS.
Updating the BIOS did not help. What finally helped was to plug in an older vid card, go into the bios and make sure the graphics portion on the bios was set to detect external pci cards.
My only issue once I had windows 10 loaded with the rx460, is that overwatch would randomly crash with the message "your rendering card has been lost".
Any chance someone knows what's going on with that?
Go to Radeon settings>Gaming>Global>Global WattMan and set Energy efficiency to ON and set power limit to +50 (max value)