It works when you are outside your home network, without the additional rigamarole of setting up a VPN for all your devices to pass their internet through your home server.

Home Adguard Home works regardless of if I'm at home or not, without a VPN. I'm on Android though and I just set the Private DNS setting - I have a domain and point it at that. I dunno if you can do Private DNS on iOS though?

NextDNS setup has an iOS(/macOS) configuration profile generator which allows you to "lock down" the dns (and use DoH).

Oh sweet this is good to know, I want to set this on my daughter's iPhone (if/when we get her one)

Pihole/adguard are great, and while their function overlaps with uBo, they are still different. You should use both.

UBo (and uBoL) have additional rules that can clean up pages. E.g. removing containers of ads.

It does much more too.

Absolutely. Pi hole does network blocking via DNS, uBoL does blocking via DOM queries.

Those are DNS only adblockers.