I was wiping this old laptop to sell or give it away. Couldn't resist putting Fedora Silverblue on it to try it out. It's very slow but I was able to check my e-mails in the browser, big win.
I didn't know there was a performance penalty to having big subnets. I'll have to look it up and shrink them.
But this is relatively moot since all my devices talk via ipv6 now. The only thing without ipv6 support I have is Mikrotik devices that only expose their management interfaces over ipv4. Anyway these are only in one VLAN, the management one.