I took a quick read of the comments and I apologize in advance if this has been suggested already.
I use a self hosted DNS server (AdGuardHome) I was using TechnitiumDNS for a long while, but moved over to the other recently so I could do some more blocking as needed (adult special needs house dweller sometimes needs limited internet). It also acts as a DHCP Server so it takes the role of both the DHCP assignments away from the router. As it so happens, this week, I got to experience the benefit of having this setup live when my main router also went down, I was able to switch to a spare router (My ISP provided one) and all I had to do was turn the DHCP off and optionally point the DNS To my AdGuardHome address, set the SSID’s up and I was in business. All of my devices happily reconnected and grabbed their assigned IP’s.
In short, if you have a spare computer, SBC such as a raspberry PI or whatnot, you can easily host something like that and not have to worry about setting those again.