ffmpeg hangs with command that used to work

I'm attempting to record video (a screen capture) on a Debian 10.4 laptop.

I'm using a command that used to work fine on Mint 19.3, on the same hardware. I'm guessing the version of ffmpeg is newer on Debian 10.4.

The command is:

ffmpeg -f alsa -ac 2 -i pulse -f x11grab -r 10 -s 1366x768 -i :0.0 -qmin 1 -qmax 1 -vcodec flv -pix_fmt yuv420p -preset ultrafast -crf 0 -threads 0 -y screen-movie.temp.flv

And the output is:

ffmpeg version 4.1.6-1~deb10u1 Copyright (c) 2000-2020 the FFmpeg developers
  built with gcc 8 (Debian 8.3.0-6)
  configuration: --prefix=/usr --extra-version='1~deb10u1' --toolchain=hardened --libdir=/usr/lib/x86_64-linux-gnu --incdir=/usr/include/x86_64-linux-gnu --arch=amd64 --enable-gpl --disable-stripping --enable-avresample --disable-filter=resample --enable-avisynth --enable-gnutls --enable-ladspa --enable-libaom --enable-libass --enable-libbluray --enable-libbs2b --enable-libcaca --enable-libcdio --enable-libcodec2 --enable-libflite --enable-libfontconfig --enable-libfreetype --enable-libfribidi --enable-libgme --enable-libgsm --enable-libjack --enable-libmp3lame --enable-libmysofa --enable-libopenjpeg --enable-libopenmpt --enable-libopus --enable-libpulse --enable-librsvg --enable-librubberband --enable-libshine --enable-libsnappy --enable-libsoxr --enable-libspeex --enable-libssh --enable-libtheora --enable-libtwolame --enable-libvidstab --enable-libvorbis --enable-libvpx --enable-libwavpack --enable-libwebp --enable-libx265 --enable-libxml2 --enable-libxvid --enable-libzmq --enable-libzvbi --enable-lv2 --enable-omx --enable-openal --enable-opengl --enable-sdl2 --enable-libdc1394 --enable-libdrm --enable-libiec61883 --enable-chromaprint --enable-frei0r --enable-libx264 --enable-shared
  libavutil      56. 22.100 / 56. 22.100
  libavcodec     58. 35.100 / 58. 35.100
  libavformat    58. 20.100 / 58. 20.100
  libavdevice    58.  5.100 / 58.  5.100
  libavfilter     7. 40.101 /  7. 40.101
  libavresample   4.  0.  0 /  4.  0.  0
  libswscale      5.  3.100 /  5.  3.100
  libswresample   3.  3.100 /  3.  3.100
  libpostproc    55.  3.100 / 55.  3.100
Guessed Channel Layout for Input Stream #0.0 : stereo
Input #0, alsa, from 'pulse':
  Duration: N/A, start: 1597616399.164690, bitrate: 1536 kb/s
    Stream #0:0: Audio: pcm_s16le, 48000 Hz, stereo, s16, 1536 kb/s
[x11grab @ 0x55f7452a4380] Stream #0: not enough frames to estimate rate; consider increasing probesize
Input #1, x11grab, from ':0.0':
  Duration: N/A, start: 1597616399.267230, bitrate: N/A
    Stream #1:0: Video: rawvideo (BGR[0] / 0x524742), bgr0, 1366x768, 10 fps, 1000k tbr, 1000k tbn, 1000k tbc
Codec AVOption preset (Configuration preset) specified for output file #0 (screen-movie.temp.flv) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
Codec AVOption crf (Select the quality for constant quality mode) specified for output file #0 (screen-movie.temp.flv) has not been used for any stream. The most likely reason is either wrong type (e.g. a video option with no video streams) or that it is a private option of some encoder which was not actually used for any stream.
Stream mapping:
  Stream #1:0 -> #0:0 (rawvideo (native) -> flv1 (flv))
  Stream #0:0 -> #0:1 (pcm_s16le (native) -> mp3 (libmp3lame))
Press [q] to stop, [?] for help
[swscaler @ 0x55f7452beec0] Warning: data is not aligned! This can lead to a speed loss
[alsa @ 0x55f74527da40] Thread message queue blocking; consider raising the thread_queue_size option (current value: 8)
Output #0, flv, to 'screen-movie.temp.flv':
  Metadata:
    encoder         : Lavf58.20.100
    Stream #0:0: Video: flv1 (flv) ([2][0][0][0] / 0x0002), yuv420p(progressive), 1366x768, q=1-1, 200 kb/s, 10 fps, 1k tbn, 10 tbc
    Metadata:
      encoder         : Lavc58.35.100 flv
    Side data:
      cpb: bitrate max/min/avg: 0/0/200000 buffer size: 0 vbv_delay: -1
    Stream #0:1: Audio: mp3 (libmp3lame) ([2][0][0][0] / 0x0002), 48000 Hz, stereo, s16p
    Metadata:
      encoder         : Lavc58.35.100 libmp3lame
frame=   69 fps= 10 q=31.0 Lsize=    2867kB time=00:00:06.88 bitrate=3409.7kbits/s speed=1.01x    
video:2753kB audio:108kB subtitle:0kB other streams:0kB global headers:0kB muxing overhead: 0.205926%

There it hangs. strace of that ffmpeg process shows:

[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1) = 1 ([{fd=3, revents=POLLIN}])
[pid 26482] getpid()                    = 26482
[pid 26482] poll([{fd=3, events=POLLIN|POLLERR|POLLNVAL}], 1, -1^C) = 1 ([{fd=3, revents=POLLIN}])

The version of ffmpeg I'm using on Debian is: 4.1.6-1~deb10u1 .

I tried removing the crf and preset, and I've also tried adding a -thread_queue_size of 512. Further, I tried -r 16 and -r 32. Some of these helped with eliminating warnings, but none of them eliminated the hang.

Does anyone know how to get this previously-working command working again?

Thanks!