Incredibly often, it seems that Safari fails to load a website. It happens both on my Mac and iPhone and has been happening for a long time. I think this has to do with my WiFi, but I fail to see anything unusual in my Ubiquiti setup.

Anyone seeing similar issues with Safari, or is this some issue in my Internet setup?

(Yes, I've tried disabling all extensions)

Private Relay was not the cause of my issues with Safari. Still seeing issues today after I disabled Private Relay yesterday 😞
@simonbs I encountered those issues when the 'Auto proxy discovery setting' for the network interface was enabled. If this applies to you, perhaps try disabling it. (I'm also using a Ubiquiti UniFi system)
@simonbs I’m a very heavy user of safari. Many extensions. Probably hundreds of tabs. Multiple windows. And I’ve never seen these issues. Maybe I’m a Safari Unicorn.
@simonbs my brain especially hurts because I use Safari for personal stuff and Firefox for work stuff, and I never have issues with Safari other than my 1password extension stops filling, requiring a restart. But several times a week I get the issues you described in Firefox.