Wacom is probably the best supported, x11-drivers/xf86-input-wacom has been around for a really long time. I'm not sure how usable it is nowadays, it's been a really long time ago since I last used it. But there's x11/libwacom for the more modern evdev approach. Can't tell you how good (or not) it works though.
Wacom Intuos S works ok via evdev on 12.2-p6, with one caveat - at least that's valid for mine: you need to have it plugged in during boot and keep it that way. Once you unplug and plug it in again, the device only seems to get power but isn't properly initiated. Needs a reboot to get it working again. Your mileage may vary with other models and different hardware/USB bus, obviously.
I believe I somehow still needed x11/xinput for it to run, but can't say for sure; it's been a while since I set mine up. Otherwise, apart from having x11-drivers/xf86-input-evdev, no config or particular addon was required,