Multi-homed doesn’t help when you have two links to two different ISPs that you want to load balance. You need NAT for that. Also, I haven’t looked at multi-homing costs but I assume they are not free (let me know if I’m wrong). Plus in a small office or retail location, you don’t need a consistent public IP when you aren’t hosting servers (or they are only via VPN).

What. If your ISP is not terrible, it just takes a route advertisement to switch the same IP address between networks. And route the same subnet through multiple networks. There is no need for OSPF, RA is good enough. The ISP just has to not filter them out and forward into routing. (You will have to inform them that you use a specific separate subnet on your network. This means typically a business contract.)

Not all ISPs offer this functionality. I can’t realistically tell the customers I manage that we can’t support their preferred provider because of this, when they rightly point out that it just works on IPv4 without need for multi-homing.

And again, multi-homing does not address load balancing / policy based routing with active active links. Eg it’s possible to have 2 Ethernet connections, 1 VDSL connection and a LTE link. Can multi-homing IPv6 work in such a situation while providing fast failover and load balancing by service/application/policy?

I wonder as well. The main downside I have heard about IpV6 until now is that many softwares are not compatible.

I have to admit there is actually some. Luckily though, when we saw problems, recent updates (i.e. mosh, ping, etc.) actually fixed them.

However there is some really broken software out there that hard codes IPv4 addresses - which even breaks NAT64/DNS64!

Which for example?

Oh, and not to forget: the ever broken cpanel.

Video games for example.

Can be fixed

mosh was such a candidate, but fortunately has been fixed