Address Reservation & DHCP Server

On my Flint V2 (GL.iNet GL-MT6000, OpenWrt 21.02-SNAPSHOT r15812+1082-46b6ee7ffc ) I used to

  • enable the DHCP Server,
  • set the Start IP Address to 192.168.8.100, the End IP Address to 192.168.8.249,
  • reserve some addresses using the "Address Reservation" outside that range (for example, my computer would get 192.168.8.30),
  • not configure anything on the device.

When I would connect, the router would automatically assigns for example 192.168.8.30 to my computer, and clients without an address reserved would simply get an ip between 192.168.8.100 and 192.168.8.249.

Now, it seems that since I've updated to OpenWrt 21.02, maybe?, this set up does not work. So, I have two questions:

On the second question, it seems that opinion varies ( https://www.reddit.com/r/networking/comments/xpxkgp/should_dhcp_reservations_be_created_inside_or/ and https://www.reddit.com/r/homelab/comments/f3d1df/do_you_set_static_ip_on_the_router_or_the_device/)

Have you tried Adguard home DHCP server?

I have not. I'm not sure how that would answer my question, and apparently I cannot activate it anyway. Even after disabling the DHCP router from http://192.168.8.1/#/lanip, it seems that I cannot activate thee DHCP server from AdGuard:

Clicking on the "Enable DHCP server" and "Check for DHCP servers" does nothing.