At work, I recently had to dig out an old NETGEAR SRX5308 ProSAFE Quad WAN Gigabit SSL VPN Firewall (that’s a mouthful) for a very specific scenario (try shotgunning four LTE modems).
Problem was, no modern browser can access the web management page due to the ancient SSLv3 standard without changes to the default security configuration, which I’m reluctant to do.
Getting an old version of Firefox. Or more specifically, getting an old portable version of Firefox.
In my brief research (i.e. downloading a few ESR versions and trying them), it seems 45.0 is the last one which will work out of the box.