I notice that the combination of Brave browser and a pi-hole slowed down several pages such that I have to wait 20-30 seconds before the page is loaded and usable.
I tried the following to identify the issue:
- Used Safari and pi-hole DNS to visit the offending page: no slowdown
- Used Brave without pi-hole DNS (by setting the upstream DNS directly on my client) to visit the offending page: no slowdown
- Used Brave with "shields down" and with pi-hole DNS to visit the offending page: slow loading
So only when I combined Brave (with or without shields) with the pi-hole DNS I got the slowdown.
I tried the suggested solution of setting up firewall rules on the raspberry, unfortunately this did not change anything.