And, while I like old hardware, the first x86-64 chips shipped in 2003. So, this is not exactly a Windows 11 situation.
Hardware older than that is going to struggle with modern browsers. A PC from that era would probably have less than 1 GB of RAM and perhaps a max RAM well under 4 GB (the theoretical limit). Using older software versions is probably best anyway.
There is so much misinformation and bad advice in this thread.
Thankfully, there are a few that correctly just say install
nvidia-580xx-dkmsYou can install new kernels after that. There is nothing to manually manage. They do not have to be LTS.