Thanks @jacadcaps for your help.
It's FTTH with 2 Ethernet ports at 1 Gbps each + 0.5 Gbps Wi-Fi (1+1+0.5 = 2.5 Gbps) via the FRITZ!Box 5530 Fiber router model
I normally use a 1 Gbps Ethernet port connected to an 8-port 1 Gbps switch, because that’s already more than enough throughput, but in this case for test, I simply connected only a PowerMac G5 directly to one of the two 1 Gbps Ethernet ports on the FRITZ!Box 5530 Fiber router (so without any 8-port 1 Gbps switch connected), and the other 1 Gbps Ethernet port is not connected to anything

In addition to attaching the log file with the debugging procedure you indicated, I’m also attaching three screenshots where you can see that MorphOS reports the negotiation as 1 Gbps, but then in terms of download speed in Wayfarer—for example, the MorphOS ISO is downloading at about 1.8 Mb/s, and also for example, the Microsoft Exchange file is downloading at about 4 Mb/s; finally, when using the TRANSFER app via SFTP SSH on the internal LAN, the speed is about 15 Mb/s.
If it were negotiating at 10 Mbps, we’d have a theoretical maximum of 1.25 Mb/s, but that’s not the case because the speeds are much higher; if it were negotiating at 100 Mbps instead, we’d have a theoretical maximum of 12.5 Mb/s, but even in this case that’s not the case because, as you can see, we’re already at about 15 Mb/s with the APP TRANSFER app via SFTP (and in any case, as I wrote in my previous message, we can even reach 20 Mb/s with the APP TRANSFER app via SFTP on MorphOS over the LAN)
So there's something preventing us from fully utilizing the full Ethernet throughput, and this is particularly noticeable when using the browser

https://gofile.io/d/LActXh
https://gofile.io/d/Rt8CS7
https://gofile.io/d/g0Mg2L
https://gofile.io/d/SehWRR

[ Edited by Divinity 11.07.2026 - 15:34 ]