2400 Mbps
I was very close to the router. Like no more than 2 meters.
It starts at a reasonable speed, but then it reduce a lot. It seems there is a buffer saturating quickly.
Resolved ! !!
Hello. I'm the original poster...
I dont understand anything in what you say, but after reading those posts, I formatted the HD in EXT4, and now it's working seamlessly on Mac. It might not be the fastest, and I would've preferred EXFAT, but at least it works as intended with all my Macs, even Apple Sillicon.
I suggest making this clear in the instructions to save others from wasting time and effort like I did. EXT4 isn't integrated into the system, so formatting directly is impossible. However, there's a free and simple way : I used the demo of Paragon EXTFS for Mac: Write/read access to Linux files under macOS High Sierra - extFS by Paragon Software for Mac
Sorry if my input seems obvious to you, but as a non-IT person, I think it could help someone like me. I didn't find it clearly stated anywhere, despite years of frustration and this question on the support forum.
Thanks to @dchao and @admon for guiding me with your initial reply discussions!
For me, this topic is now resolved.
can you update the samba to use samba(7) then we can use the settings here for osx Configure Samba to Work Better with Mac OS X - SambaWiki