Sorry for the delay - your answer slipped past me.
alias-clients are not required to show hostnames instead of IPs.
That experimental feature will aggregate dashboard statistics for several IP addresses as aggregated by a network interface's hardware address under a single hostname. Your observation is expected: It's effect is limited to the dashboard.
However, associating client IPs to hostnames is done automatically by several other means like regular reverse lookups for client IPs or inspecting directly observable, same-link network information.
If you were not seeing hostnames in Pi-hole's dashboard, then there must be a separate reason for that.
If your router is your DHCP server, using your router as Pi-hole's only upstream or enabling Pi-hole's Conditional Forwarding would be required for reverse lookups for local IPs to succeed. Of course, this would imply that your router would not only know the names for its DHCP clients, but that it would also provide those names as replies for DNS queries.
Note that not all routers would do so.
You may verify whether your router at 192.168.8.10 does by running a reverse lookup past it, e.g.
nslookup 192.168.8.6 192.168.8.10
Another fundamental prerequisite for seeing individual clients (IP or hostname) in Pi-hole's dashboard is that clients have to talk to your Pi-hole directly.
Your debug log shows your router's DHCP server to distribute your Pi-hole as local DNS server to DHCP clients - but also 1.1.1.1:
*** [ DIAGNOSING ]: Discovering active DHCP servers (takes 10 seconds)
Scanning all your interfaces for DHCP servers
* Received 300 bytes from eth0:192.168.8.10
Offered IP address: 192.168.8.166
DHCP options:
Message type: DHCPOFFER (2)
router: 192.168.8.10
dns-server: 192.168.8.5
dns-server: 1.1.1.1
--- end of options ---
That would allow clients to use 1.1.1.1 for DNS at their own discretion, bypassing Pi-hole completely. Pi-hole has to be the only DNS resolver for your clients.