Set a static IP on the box. You shouldn’t be relying on DHCP for a service you need consistent access to. Tools exist to scan for other IPs on the network and once you have a list it should give you an indication of where the DHCP lease starts (eg you may see 192.168.0.10-192.168.0.13, 10.0.0.100-10.0.0.148, etc) and you can set an IP far outside of that lease, after pinging to make sure it’s not in use.
If I wasn’t in control of DHCP, that’s what I’d do. It’s possible you’ll hit a conflict one day but not very likely; if you did it’d be easier to resolve with a change of IP than a reboot and wondering where the server has ended up now.
Do keep an eye on it. Even if you did have to reimage the SDCard (which everyone will eventually, SDcards do fail often) you can set it back up without resetting disks. See: Nextcloud Box OS images