I had the same thing happen to me after a BIOS update this morning. Nothing would show up on the screen, and I kept trying to bring it back with a hard reboot. This didn't work, and I was looking at opening it up to remove and reconnect the battery cable as [NAME] suggested. Turns out I didnt have to do that, and I was able to recover the BIOS using this guide -- [URL]  
My Dell G15 5515 Ryzen Edition got bricked after lates BIOS update, all went OK but after the last reboot the system wont do any post, I contacted support saying that as me, many others over the internet are saying the same problem, this is very recent, the update went online on may 8 of 2023 and they didn't say anythin else than "send us your laptop for 39,99$"    This is the BIOS [URL] now I have a 1000$ paper holder   I'm creating this post so it can be indexed and maybe someone else can see it and provide with a solution
Dell G15 5515 Bricked after latest BIOS upgrade MAY/2023