We know that not even the latest versions of browsers for Windows 98 support HTML5 Video. So we used Opera 10 + Flash 9, until Youtube stopped supporting Flash. But I found the solution that was to install KernelEX in Windows 2000 mode and install Firefox 12 that had support for HTML5 video. Until a few weeks ago it worked, but until then it worked, then it put me error of reproduction, I do not know if there is a way to see YouTube in Windows 98 after all this, it will be that you will not be able to see Youtube anymore in Windows 98

So far, we have no workaround for Youtube. There is one (https://msfn.org/board/topic/177485-backporting-newer-browsers-to-win9x-with-kernelex/?do=findComment&comment=1154915) of diamant, it is inconvenient but working. Commodore's finding has given me basically nothing useful, see some posts later. The procedure had worked only for his test video and not for others. FF9/10 and Opera 11/12 aren't vp8_only_browsers. Now FF 43 is required to see youtube videos.  By the way, you would be the first to make FF12 run stable on 98.