PieterBased on further feedback I got, I went for the Yealink SIP-T46S, an "ultra elegant" IP phone. (Props for printing that even on the box) The Yealink phones are said to be among the best, even if more expensive than the Grandstream phones which lead on price/value.
I like that it doesn't have that many fixed-purpose keys. And the ones that are there are subtitled, albeit in English. Still better than not really self-explanatory icon only keys.
A first glance at the Webinterface. Germans judge for themselves about the quality of the translation.
While the Webinterface reacts quite quickly (compared to e.g. my FritzBox), it's a bit confusing and over-loaded. I don't have e.g. a GrandStream or Cisco WebUI for comparison available, but I'll assume that all IP phones suffer from detailed configurability.
For example, I wouldn't have expected the Firmware upgrade functionality below "Settings".
Haha, you can even upload your own localization files 😂 I *WONDER* why that feature exists 😂
Currently skimming the "Yealink SIP-T2 Series/T4 Series/T5 Series IP Phones Administrator Guide". 622 pages. #asonedoes
So here's my summary for now: it is a very, very powerful VoIP phone but I think I got it to the point where I can sell it to my customer as "ready to use". My SIP test account worked immediately out of the box. Everything I wanted to tweak I could tweak.
Except for a single optical-only thing: I'd like the date to be displayed first on the idle screen, then the current time. There is currently no option for that. BUT: Yealink uses a ticket system where I just simply created a ticket for that. Let's see if it gets a chance.
The simple fact that I was a new 0815 users can submit a request for it, paired with the fact that I could get everything off the Website I needed (manuals, firmware) easily, speaks for Yealink (but not against Grandstream, rather against Cisco).
The default German localization could use some work and the phone's Web interface is a confusing mess that needs more visual organization (categories and sections). But all in all a well-engineered product I'd say (although I miss experiences with other vendors, as mentioned).
Oh, and yes, of course I'm aware that any professional configuration will be done via (luckily plain text) config files resp. deployment mechanisms. Even then however the Web UI should aid the occasional user that relies on it and be more than a dump of input boxes.
Reply from Yealink in ticket system:
"For this feature request, I afraid that our PD would deny it.
For current user experience, it's decided after investigation with our customer."
I don't get what that's supposed to mean? Who is "our customer"?