I was doing some quick research and saw someone suggest installing each OS with the other drive disconnected. That way you can first get each one working individually and there’s no chance of one messing with the other’s bootloader.

Do you have the os-prober package installed? I haven’t used Fedora in over a decade, so I don’t know if it’s a default or not.

Support for Archos devices was removed from daily builds in 2020.

I have a Thinkpad T480 that I’m very happy with. I believe it’s around 7 or 8 years old, but it works great. Unlike most laptops, it doesn’t have soldered RAM, so it’s easily upgraded. One downside is that most units don’t come with a lot of storage, so you’ll probably want to get a larger drive. I spent around $200 on mine plus another $100 for the SSD. It’s a great inexpensive laptop that’ll last for years.