SnowLeopard is my personal use-it-every-day OS.
I have spent some time making the main toolchains work quite well on SnowLeopard, and you will find on MacPorts a collection of clang versions from clang-3.3 to clang-11 that work well.
There is also a nice, fairly recent, libc++ that installs onto SnowLeopard and lets it do things that even more recent macOS versions have trouble doing.
On the gcc front, we have apple's gcc-4.2 all the way to gcc11 (current).
The cctools and ld64 versions available for SnowLeopard are very recent (Xcode 11 vintage).
I ported over the last possible (so far) version of qt5, qt5.3, that we could make work to SnowLeopard. Some newer versions of qt5 would be nice, but the workload curve arcs up sharply.
qt4 works great, and supports quite a lot of software still.
Finally, there is a compatibility library I have been working on called legacysupport that makes the SnowLeopard SDK responsive to features that were often introduced in much later SDK versions (time functions, etc). This lets a lot of quite current open-source software install and work well on SnowLeopard.
Things like Octave, CherryTree, a nice collection of qt5 software, a lot of open-source games, and almost all of the current tools (pdftk, apache2, mysql, etc, etc) work just great, very solid.
I ported TenFourFox to Intel with Riccardo's help back in 2018 and have uploaded the Intel builds since then (built on Tiger Intel for maximum coverage). That ship is unfortunately coming to an end as upstream has no plans to do any significant updating to that branch any longer.
However, I do have webkit2-gtk working on SnowLeopard, and some of the linux browsers (epiphany, for example) will build and run on SnowLeopard (imperfectly so far).