Still have one, still works. Would happily use it if it were still practical. I think you can still load OpenWRT on them, but there's no software route around the hardware being outdated and slow.
Not a recent version, not from the last 10 years at least. They dropped even 8/32MB devices. On my Turris Omnia, the bare system with nothing else running takes about 70MB RAM, mostly because of kernel size. Linux itself isn't as light as it used to be.
The best you can do is put DD-WRT on it. AFAIK, they still use kernel v2.6 on devices this old.