There is no need for an old switch. I've connected my SE/30 with an Asante/Net card to many modern 1000/100/10 switches that I have in my house. Cisco and Netgear. Every switch I've ever seen goes back down to 10bT...
Now, I wouldn't plug it directly in to the router, but get a $20 1000/100/10 Netgear 5 port switch on Amazon, so you can use it for other things.
As for DHCP your Se/30 with MacTCP isn't going to do it. Maybe OT will get an address, but MacTCP you need to manually configure it. At least my MacTCP won't pick up any DHCP offers from modern versions of dhcpd.
Now, I wouldn't plug it directly in to the router, but get a $20 1000/100/10 Netgear 5 port switch on Amazon, so you can use it for other things.
As for DHCP your Se/30 with MacTCP isn't going to do it. Maybe OT will get an address, but MacTCP you need to manually configure it. At least my MacTCP won't pick up any DHCP offers from modern versions of dhcpd.