Everytime I run pihole -up this line scrolls by :
[✓] Detected AArch64 (64 Bit ARM) architecture
Which really bothers me…
IMHO it’s either AARCH64 or aarch64 and not this weird “hybrid” that AFAIK no one uses ?!
Could this be changed to one of the above ?
Please ? Pretty please ?? 
Just to make my answer clear:
I'm not sure if there is an "official" naming rule, but I think the name of the architecture is "AArch64". This is what the installer is doing. It shows the architecture name.
When used as part of a software package name (which usually uses lowercase letters), I often see aarch64.
This is similar to PHP.
The language name is "PHP", but Linux packages always start with php.
OK, AArch64 it is then! 
It seems this is one of those “How the people on the street call it” vs. “How it’s officially called” things and somehow the former seems to be used more often than the latter…
The PHP example is not a big deal IMHO but this just looks so weird… Oh well… My bad! 