I actually have 2 things to add. It'll be a long comment, and afterwards, you can message me or comment here and I will help you if you have issues turning your pc on with a ryzen cpu

First thing will be how to flash a 5000/5000G series (5600G/5700G) on AM4 boards featuring a Flashback button like my Asus TUF B550M-E WIFI. But any cpu would work similarly.

Second, when you are at your wits end, broken inside and desperate cause your new Ryzen PC won't post or boot, trust me, you are not alone in this and I'll try to help. I had 4 days of pure hell that my stomach hurt from stress cause I poured all my money into a PC that didn't work even when all components were brand new, all was plugged in correctly and each component was working on its own. I'll write my story down below.

1 - HOW TO USE FLASHBACK

This is purely for the guys who can't turn their PC on, monitor says "no signal" and the PC acts like it's dead. Its 99% the Bios. Or something is broken like mobo or psu. The new 5000 series Ryzen CPUs aren't recognized by most boards out of the box. You need to flash the bios. You do this with either a 3000 ryzen cpu (which ofc most of us don't have) or a flashback button. Newer boards have a button at the back where the USB and display ports are. Usually it's at the top. It's called a flashback button and allows you to flash new bios you need without a cpu.

To flash the board so it recognizes your cpu, which is why the pc won't post or boot most of the time, you need to go to the official manufacturer website and download the new/newest BIOS. For Asus, you download the bios file and with it the Asus renamer app gets downloaded too.

MSI bios file needs to be renamed to "MSI.ROM" Other manufacturers work siniakrlyy just check their support site.

Once the bios is downloaded to a pc, extract it and run the renamer app. It will automatically rename the downloaded bios so the board recognizes it via its name. In my case, it renamed the asustufb550biosfile to "TB550MEW.CAP" which is whorter for TUF B550M-E WIFI. It might show the renamed bios file without the affix like "TB550MEW", that's OK. Once it's renamed, copy the renamed bios to a FAT32 formated USB. It can be USB 2.0 or USB 3.0, doesn't matter. You just need to copy the bios file directly onto the USB without a folder. Basically to the "root of the USB". Once it's on the USB, you need to put it in the BIOS USB port. It's usually not directly under the flashback button. You have maybe 6 USB ports on your motherboard but only one USB is the correct one. On your mobo backplate, it shows which it is. If you don't have a backplate (doubt it), it says so in the manual.

Once the USB flash drive with the renamed bios is in the correct USB bios port, you need to press the flashback button for 3 seconds, then you release it and it will blink for 4-5 minutes in a green or red light. That means it's flashing the bios. And once it stops blinking, you have a Ryzen 4000/5000/G supported board.

HOWEVER! YOU DO ALL THIS WITH NOTHING ATTACHED TO THE BOARD, JUST THE USB WITH THE BIOS AND THE PSU (POWER SUPPLY)

Your psu is connected to the outlet and connected to the mobo with just 2 connectors : 24pin (main power for mobo) and 1x4pin/2x4pin CPU power cable. Nothing else is attached. No CPU, no drives, RAM or GPU! Just PSU and Board are used to flash the BIOS + the USB with bios.

Once the bios flashback light stops blinking, you switch your psu off (with the button, if it has one) and take out the USB flash drive. Then you connect the CPU with cooler (no need to screw it down yet, it's a test), and just one stick of RAM - if you have 4 RAM slots, put it in the second farthest from the CPU socket in B1 (from cpu A1, B1, A2, B2) You still don't connect drives or fans. You just want to test the bios. If you have integrated GPU on CPU (iGPU on APU), you don't even put in a dedicated GPU. You connect the monitor and turn the PC on via case or screw driver (look "How to turn pc on with screw driver" on YouTube). If it shows option to enter bios, you are good to go. If it doesn't show after few seconds, take the cpu out and place it back and try to boot again. Once the bios shows, connect everything install Windows/Linux and have a nice day. If it doesn't.... Read number 2:

2 - WHAT HAPPENED TO ME - ISSUES YOU MIGHT ENCOUNTER

I have build many PCs, both for home or gaming. I flashed bios many times. Never have I had so much issue with a new 2021 cpu like the 5600G (280$) and a new Asus B550 board (120$). When it at first didn't work, I was baffled for a second, then realized the bios needs flashing. I thought, I will flash this mobo and I'll have a working gaming PC ASAP by the time I drink my coffee. Well, 4 days later, 3 boards tested, 250 miles driven from home to tore to friend and back in heavy xmas holiday traffic, I was on my 20th coffee, head ache pills,almost crying grown ass man and my eyes hurt from all the tech sites and videos. My shoulders hurt form dismantling 3 PCs (one was my friend's pc) like 8 times! So why didn't an 800$ mid range gaming PC with superb specs all brand new, work? Well... PC case... Yes. Pc cases.

Flashed the b550 bios with 3 different bioses. Nothing. Used friends ryzen 3600 build and B450 gigabyte. Nothing. Used shop's MSI B450 mortar Max. Worked. Put it back into case. Didn't work. Returned it for an msi B450 tomahawk Max. Worked. I put it into a different case. Worked. Disconnected psu cables and put inside my case....nothing. I was about to break from the stress. I just couldn't figure out why new pc with appropriate bios doesn't boot or post. I flashed the board 3x and it worked and then shortly after didn't. And then I read something about static electricity and I couldn't believe it. The 1st board I got, the Asus tuf B550M-E WIFI, which I wanted to return as faulty or whatnot, after 4 days of other boards, Worked for the 1st time...outside the case, I was so happy. Then I put it into my main case. And it didn't work. Then I learned about the static electricity or something. Sounds stupid absurd silly. Sounds like I'm writing this out of my ass! But it was just that! and since I cleaned the case with water damped towel, it works flawlessly.

Summary:

It is the outdated bios, but then it was the case. You need to flash the bios, but a lose cable or anything I mention above can cause the pc to not post or boot. Some older PCs can boot into bios without cpu, ryzen won't. I learned that the hard way after watching confidently a YouTube video "how to boot pc without cpu or ram" So apparently, the very first day I did flash the board correctly, but a case just prevented me from everything. I pointlessly dismantled friends pc, spend 40$ on gas, made me kinda sick and feeling like dying for 4 days.

For any questions contact me. I'll help you work this out. I've seen hundreds of posts like this by people desperately trying to solve this mess