It would be welcome should the chromium-legacy project at least make it reasonably feasible for anyone to compile their own binary to run in a 64-bit SL setting — even as pre-compiled binaries generated for download are intended for 10.7–10.9 users (i.e., a “roll your own” proposition).
I mean, if it was supported in the source code, it wouldn't be any extra work to change the deployment target in the binaries that are built automatically.
Chromium Legacy is different from e.g. TenFourFox in that it isn't intended to be compiled on the same OS that it runs on. You actually need a Mac (or a VM) running 10.15 (Catalina) or newer in order to produce a binary. It's just that this binary is able to run all the way back on 10.7.
I know it's frustrating that there's no Snow Leopard support, but we'd just need someone with the requisite time and experience who was willing to do the work.
If you have the time and inclination, you might try it yourself. First, get Chromium Legacy to build for 10.7, so you know you have that process down. Then, try changing the deployment target to 10.6, and see where the build fails. Then, go through and fix the errors one by one, using the code from older versions of Chromium as a reference. You don’t necessarily have to understand what all the code does, just enough that you can do some pattern matching.
It will absolutely be difficult and frustrating, but you may learn a lot along the way! This was my experience updating Perian to support VP9 and HEVC, it was out of my league when I began but I just kept plugging away at it until it started to make some kind of sense.
The biggest initial hurdle may be that you do need access to a modern Mac—and a fast one at that, because Chromium builds take
hours to complete! Getting Chromium to actually
build on an old OS would be a major project in itself, and it isn't necessary.