Τry these instructions, maybe they will help you https://support.mozilla.org/en-US/kb/how-to-set-the-home-page

I really appreciate your response, thank you. Sadly it does not work for me. I am on an Android tablet (Samsung) and tried to use the section "Set or change your home page through the Home button." I only see one tab at a time and it will not let me click and drag that tab anywhere. The options on the setting the home page area do not include using the current page like they used to. I remain stymied.

The homepage for firefox for android works differently than the computer. Read this article I think it will help you

https://support.mozilla.org/en-US/kb/customize-firefox-home-screen

Thank you. Yes, I had already worked through that page. I simply want to set my homepage to open YouTube when I open Firefox. Best I can see (or find through trial and error) there is no way I can do that. Has it changed? I used to have it set that way.