So, as I understand it we've answered some of these questions before, but probably would be a good idea to get the answers in a more public space.

Firmware updates are a known hassle. We're working with IBM on a better update mechanism, but it's not our top priority at the moment.
Boot time is also something we try to improve, in conjunction with IBM and the overall community. Progress is slowly being made there; it's all software/firmware, so you don't have to worry about any hardware changes required to improve boot speed.
We're waiting on the Broadcom firmware still; my understanding is there's one bit of setup that isn't fully understood yet, but once that's figured out we can switch over
Graphical installers are available and work. Fedora just enabled workstation builds, see
https://www.talospace.com/2020/01/fedora-workstation-live-isos-up-and.html for info. Adelie has a workstation installer too:
https://www.adelielinux.org/Firefox is really the largest project to have a somewhat embarrassing lack of full support (specifically, the JIT). Google has also continually refused to merge our POWER patches, though due to Chromium's popularity the POWER support has been reliably maintained anyway out of tree and in Ungoogled form as well, see
https://github.com/leo-lb/ungoogled-chromium (and huge thanks to the maintainer for doing this!)
Yes, the HDMI fix is still required. We don't have a kernel patch yet.
Regarding Glamor, that's a software problem. There is no "Blackbird 2" planned for POWER9, and POWER10 is still a significant distance away.
So far as I know Vikings will be launching our products soon-ish. I don't have exact timing, you could always write them and ask.

Does this answer your questions?