lots of low end switches use RTL837x series as basis nowadays

its basically AISC plus microcontroller - https://svanheule.net/switches/rtl8370

I love https, but I also hate that its basically killed on-site caching and give CDNs more power as its only way to distribute content closer to user

First time, eh? I remeber namecheap had problems 10 years ago when they upgraded interface and something was wrong with dns srv records. So i had to move out to gandi at time

eh, you can just add search domain via dhcp or static configuration and just type out http://mything/ no need to enter whole domain unless you need todo ssl

Diameter in mobile network is heavy user of SCTP, but from what I've read they moving away from diameter into HTTP calls for 6G.

For communication between carriers and some communications within a given carrier's network components, yes. Base stations all still communicate with the core network over SCTP, though.

As previous owner of Archer C7, Archer AX23 barely upgrade if you want to install additional packages as it have same 16/128 flash/memory configuration just like C7.

Personally I upgraded to xiaomi Router AX3200 with 128/256 flash memory configuration and 4:4 MIMO, though it lacks USB and have WAN+3LAN ports compare to usual WAN+4LAN.

SCTP still have some donwsides it has to resolve https://http3-explained.haxx.se/en/why-quic/why-tcpudp#why-n...

Plus we need happy eyeballs for transport if SCTP run over IP and not encapuslated https://datatracker.ietf.org/doc/html/draft-grinnemo-taps-he

But IPv4 pretty much non-workable since most end-users behind NAT and there no known implementation to work around that.

SCTP works fine on internet, as long your egress is comming from public IP and you don't perform NAT. So in case IPv6 its non issue at all unless you sit behind middle boxes.

Probably best approuch would be is like happy eye balls but for transport. https://datatracker.ietf.org/doc/html/draft-grinnemo-taps-he

How many corporate or residential firewalls are configured to allow SCTP traffic through?

residential - not many. Corporate on other hand is different story, thus why happy eyeballs for transport still would needed to gradual rollout anyway.