Could you also share whether your Pi-hole's 192.168.5.18 or its virtual :: holds accountable for the 2,603 requests topping the list?
Hovering over the pi.hole name in that line form your dashboard's Top Clients should reveal that information.
That :: virtually is your pi.hole, as the network table states.
If you had DNSSEC enabled, that would nicely explain why you would see quite a few requests of types DS and DNSKEY originating form your Pi-hole.
You could use the following command to see some examples for that:
grep dnssec-query /var/log/pihole.log
Visibility of those type of requests in the Query Log was added with Pi-hole FTL v5.9, Web v5.6 and Core v5.4 released.
For an in-depth explanation of Pi-hole's inner DNSSEC workings, see also Understanding DNSSEC validation using Pi-hole's Query Log.
If your requests do not seem to be associated by DNSSEC, please share some lines from your debug log. A command like the following may help you with that:
(please adjust as necessary)
grep "from 192.168.5.18" /var/log/pihole.log