I have a suspicion that the kind of surge protector rating it’s reasonable to fit to the main electrical input for a building is unlikely to actually trigger on the small surges that the surge protector in a UPS will, and you will still get earth-leakage trips on the RCDs with UPSs downstream of them.

Having one radial (for the computer rack) NOT protected by an RCD seems like a cheaper and more reliable solution, but I confess it’s not bubbled to the top of my to-do list yet to get a sparky involved for advice.

You understand that the RCD is (mandatorily) in the electrical distribution panel where it hands off to the utility supply right?

Although it’s an absolute pain in the arse in certain scenarios. Surge protectors essentially present as a leak to earth any time they do their job, so my mandatory RCCBs on every circuit turn minor mains fluctuations into permanent outages.

I really need to see if I can legally run one circuit that isn’t RCD protected for my homelab…