Provider of the physical media (光回線) and the connectivity provider ontop (プロバイダー) are separated in Japan. I'm on NTT flets for physical: a fiber cable goes into the whole building, into a delivery room (MDF室). From there fiber runs to my room. From there, one has these options:
Ontop of the physical connection, an IP provider has to be contracted. I'm with Biglobe, did not care to much about this when subscribing - but payed attention they offer IPv6, which I had to explicitly enable with an option on a website. Biglobe seems focused on normal end customers, so changing IPv4 addresses are to be expected.
In 2024, I got aware that plain modems were possible - so got one and returned the “home gateway”. For router, 2 devices were interesting:
The Linksys is much cheaper, and even if buying the GL-MT6000, it would not offer the upcoming Wifi7.
Taking the Linksys into usage, installing OpenWRT, was quite painless with exception of IPv6: with the homegateway, I think I had a complete IPv6 segment delegated to my LAN, and was running IPv6 services like SSH, webserver. The router did no packet filtering. With the Linksys/OpenWRT, I get via DHCPv6 delegated an IP with /64, but not a bigger segment.
There are other ISP/IP layer providers which can be used and offer static IPv4 IPs, for offering services - details are here.
opkg update opkg list opkg install atop opkg list-upgradable opkg upgrade wireless-regdb urngd