Firefox reportedly only ended support for 2001 OS Windows XP (and Windows Vista) in 2023, which means a pretty impressive 19 years of support (accounting for Firefox 1.0 releasing in 2004).
Acer's Veriton NUC AI packs lots of ports and gets the job done as a mini PC for basic work, but you can easily find much faster compact desktops for the same price or less.