The closest open-source alternative for frame generation on #Linux is #MPV with #Vapoursynth and #MVTools. I still haven't been able to configure it in such a way that there's not a lag of almost a second, though.
I know it's niche, but I'm not happy about frame generation still depending on proprietary software on #Linux. It's either #LosslessScaling / #LSFGVK (proprietary engine, interface moved from free software to non-commercial), or #BorderlessGaming (used to be free software, then moved to proprietary)