This has nothing to do with SDL. There is no MUI version, but this uses Reaction.
Ah yes, that's right.
I'd test this, unfortunately my Amiga is currently in the "need to figure out why the mediator won't work and gives me memory errors after swapping the Kickstart for the custom one that supports the 060 being plugged into the A3640" and my Falcon doesn't have an 060 in it yet. Granted, I have yet to try getting netsurf running on it either, though I do have it Internet connected.
I do think Netsurf is the future for 68k browsing. Though from what I can see, the latest port to the Atari is 2.9, vs 3.5 for the Amiga. Hell, even Debian doesn't have a newer package than 3.2
P.S. Maybe 3.5 build is only for AmigaOS 4? I am pretty sure the last time I tried it on my A4000, it was 3.2 or so.