I had the same problem with a Govee RGBWW Led bulb; without buttons. Thanks to this post I tried suggested steps but didn't work at first.
In my case steps to get success were (after several tries):
H6008 series bulb:
0 - If you linked the bulb in Google Home (or other assistant), unlink it by using option of linking, and unlink account, in that app.
1 - Remove device from Govee app.
2 - Hold switched on the bulb at least 5 seconds, (Switch off one second, Switch On) x4 times.
3 - Light flashes.
4 - Add device into Govee app again.
4.1 - Add wifi (perhaps it's better SKIP this step; see 4.3)
4.2 - Take note of QR code in Matter section.
4.3 - Do "Network Reset".
5 - Use mobile app Home Assistant Companion app.
6 - Go Settings → Devices and Services.
7 - Click on "Add integration".
8 - Click on "Add Matter device".
9 - Click on "No. It's new" option.
10. - Use QR code saved on step 4.2
11 - Now, when screen "Get ready for Set up" is shown, switch off very shortly and switch on bulb. If light of bulb doesn't get off (although you switched on) repeat until that situation occurs and quickly click next button to see if finds device and register on Home Assistant.
If there is no luck retry repeating from step 10 or so, it could work.