Adobe letting Lightroom "Classic" sit and rot for years, along with increasing the price substantially has really opened the market up to competition. I'm currently using PhotoLab 4, but that's mostly because workflow wise it is "good enough" while offering killer features like DeepPrime and ClearView+ (that neither Lightroom Classic nor Darktable have an answer to yet).
Long term though I suspect Darktable will be the final victor if they can find a consistent group of contributors. The biggest limitation right now is lack of proprietary plugin support, for example if they had PureRaw Plugin support I could use Darktable instead of PhotoLab 4 today.