Earlier quoted context omitted.
I hope those scada systems aren't running on regular Windows. If they are, they should be running on Win10 LTSB on 32-bit so they should keep working till at least 2025 if XP's level of compatibility was good enough to run them. If they can't be run on that, there's still MS-DOS licenses being sold and FreeDOS might also serve them in a pinch. If a system is not maintained for long enough that it's still running in c…
What if the manufacturer doesn't exist anymore?
Just keep running the older version of Windows that worked with the device. Add a couple of layers of configurations, firewalls, VPNs, traffic monitoring and whatnot inbetween to reduce the risk and don't connect the device to the internet. Your solar panel farm doesn't need to access Gmail or run Windows 10.
Your obscure SCADA device is your responsibility. The switchover to 32bit had been announced 20 years ago and the switchover to 64bit 10 years ago.
Also, if the manufacturer doesn't exist anymore, where are you going to source replacement parts?