Using Router mode. Guest Network seems to be working just fine. I am trying to change the default network to a 10.x.x.x one, but I have to edit the config files to do so.
I think I reproduced it reliably. I can save Router IP Address == 10.10.10.1 or 10.10.10.2, but saving 10.10.10.200 does not work and reverts back to the original IP before the change and the services do not get restarted.
I can confirm that for TOS4.x beta 2. if the last digits exceeds 22 it is not working any more from Foris. No issue via clie, e.g. uci set network.lan.ipaddr='10.10.10.200' && uci commit or LuCI.
Seems it bug and since this being a user forum you might want to lodge it with the developers https://gitlab.labs.nic.cz/groups/turris/-/issues