I have a setup where I need to connect to a fritzbox for internet access, I looking for a 802.11ax router which supports OpenWRT and fully supports client or client bridge mode. I want to use this router as a CLIENT to connect to the remote one, not as a WDS.
I have found some posts that broadcom chips have an issue with this mode.
There is no such thing as "Client Bridge" in standard 802.11 (WiFi) networks.
Broadcom chips are least supported - and unless you have one supported by brcmsmac or brcmfmac they won't work at all and there are no ax devices with broadcom wifi supported on OpenWrt.
Any router with ax wifi chips that use the following drivers should support all of the client, client wds and 11s mesh modes: mt76, ath11k
Use any router that uses the drivers above (I don't see any router in your list that doesn't support client mode), and you have the following options:
use it as a router where WAN side is going to be the wifi client and have a separate lan
use wds or 11s mesh (not possible if upstream router doesn't support it)
use relayd to achieve what most vendor implementations for extenders do
use the kmod-trelay package that can only work if you have only one device connected to the lan port and clone it's mac address for the wifi client.