This is a long story. I use an old OSX 10.4.11 machine (Power PC) as a web server. Very low use. It runs X11 at 1.1.3 (XFree86 4.4.0).
For several years I used X-forwarding to show log traffic on a newer Mac Intel machine (Mac mini). At some point after about 2006 this just stopped working. I have never tried to upgrade the 10.4.11 machine as it met and continues to meet my needs for a low cost Web server.
Meantime XQuartz has come and been through several new versions, as has MacOS. Currently I have MacOS 10.13.6 and XQuartz 2.7.11 on the Mac Mini. I am revisiting why the long-defunct X-forwarding sessions to OSX 10.4.11 stopped working.
I find I can do X-forwarding fine from my Linux 18.04 box, which was a surprise. I have spent a lot of time trying various approaches to resolving the issue. It occurs to me that the 10.4.11 setup may just be too old, and therefore incompatible. Hence my question: "mac osx 10.4.11 with x11 1.1.3 (XFree86 4.4.0) - is this compatible to do X-forwarding from Mac OS 10.13.6?".
Any comments will be much appreciated.