The command:
ffmpeg -y -vsync 0 -hwaccel cuda -hwaccel_output_format cuda -resize 1920x1080 -i "Infinity.mkv" -vf "ass=Infinity.ass" -c:v h264_nvenc -preset slowest -crf 18 -c:a flac -af aformat=s32:48000 -compression_level 5 -strict -2 Infinity.mp4
results in:
Impossible to convert between the formats supported by the filter 'graph 0 input from stream 0:0' and the filter 'auto_scale_0'
Error reinitializing filters!
Failed to inject frame into filter network: Function not implemented
Error while processing the decoded data for stream #0:0
Conversion failed!
I tried adding hwupload and hwdownload to the vf filters. The result was the same.