Bodhi linux is ubuntu/debian based (but no snaps out of the box) and is good for older hardware both because it is lightweight and because it has support for 32 bit architecture, but it comes bundled with chromium not firefox, but you can easily install ff (or even better librewolf) and remove chromium.

Also there are bsds - I don’t know about Bottles and Inkscape but you might be interrested to try out NomadBSD which is for USB boot but can also be installed on hardware, it is freebsd based and comes bundled with FireFox+UBlockOrigin (altho it’s an older version you’ll need to update the packages)

They are referring to the original software and protocol of Soulseek not the slskd one in the link, no?

Try Bodhi Linux - you can burn it to CD/USB or copy it on a Ventoy USB stick to test before installing and it is available for 32 bit systems