Some exceptions. Also jbig2 vs. jbig2enc.

[DiagonalArg]

Looks like a nice tool, thanks. I'm running scans2pdf on the output of scantailor-advanced. Some exceptions occurred, so here is the output of running it on the first page. I can provide the image if it would be useful.

Note that ubuntu 22.04 has a snap providing jbig2enc, while you're looking for jbig2.

$ scans2pdf -v Feigon-001-000.crop_2R.tif scans2.pdf
WARNING:Program not found: jbig2
DEBUG:Using selector: EpollSelector
DEBUG:Running command: ['convert', '-colorspace', 'sRGB', '-profile', '/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/argyllcms-srgb.icm', '-background', '#ffffff', '-alpha', 'remove', '-alpha', 'off', '-type', 'TrueColor', '/home/user/Feigon-001-000.crop_2R.tif', '/var/tmp/djpdf-xwxq05cu/image.png']
DEBUG:convert-im6.q16: profile 'icc': 'RGB ': RGB color space not permitted on grayscale PNG `/var/tmp/djpdf-xwxq05cu/image.png' @ warning/png.c/MagickPNGWarningHandler/1668.

DEBUG:Running command: ['convert', '-fill', '#000000', '-opaque', '#000000', '-fill', '#000000', '-opaque', '#000000', '-threshold', '0', '/var/tmp/djpdf-xwxq05cu/image.png', '/var/tmp/djpdf-nma9ouby/image.png']
DEBUG:Running command: ['identify', '-units', 'PixelsPerInch', '-format', '%x %y', '/var/tmp/djpdf-xwxq05cu/image.png']
DEBUG:Running command: ['convert', '-fill', '#ffffff', '-opaque', '#000000', '-resize', '50%', '/var/tmp/djpdf-xwxq05cu/image.png', '/var/tmp/djpdf-_4oeppyf/image.png']
DEBUG:Running command: ['identify', '-format', '%w %h', '/var/tmp/djpdf-xwxq05cu/image.png']
DEBUG:Running command: ['convert', '-format', '%c', '/var/tmp/djpdf-nma9ouby/image.png', 'histogram:info:-']
DEBUG:Running command: ['convert', '-format', '%c', '/var/tmp/djpdf-_4oeppyf/image.png', 'histogram:info:-']
DEBUG:Running command: ['convert', '-fill', '#000000', '-opaque', '#000000', '-fill', '#000000', '-opaque', '#000000', '-threshold', '0', '/var/tmp/djpdf-xwxq05cu/image.png', '/var/tmp/djpdf-0h9szie5/image.png']
DEBUG:Running command: ['tesseract', '-l', 'eng', '--dpi', '600', '/var/tmp/djpdf-0h9szie5/image.png', '/var/tmp/djpdf-hogdbirb/ocr', 'hocr']
DEBUG:Tesseract Open Source OCR Engine v4.1.1 with Leptonica

INFO:Can't extract textangle from ocr_line: bbox 716 941 826 987; baseline 0 0; x_size 61; x_descenders 15.25; x_ascenders 15.25
DEBUG:Exception occurred:
Traceback (most recent call last):
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/hocr.py", line 46, in extract_text
    textangle = textangle_regex.search(line.attrib["title"]).group(1)
AttributeError: 'NoneType' object has no attribute 'group'

INFO:Can't extract textangle from ocr_line: bbox 643 1005 898 1043; baseline -0.008 -6; x_size 37; x_descenders 7; x_ascenders 8
DEBUG:Exception occurred:
Traceback (most recent call last):
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/hocr.py", line 46, in extract_text
    textangle = textangle_regex.search(line.attrib["title"]).group(1)
AttributeError: 'NoneType' object has no attribute 'group'

DEBUG:Running command: ['convert', '-alpha', 'remove', '-alpha', 'off', '-colorspace', 'gray', '-threshold', '50%', '-compress', 'fax', '/var/tmp/djpdf-nma9ouby/image.png', '/var/tmp/djpdf-82nt536j/image.pdf']
DEBUG:Running command: ['qpdf', '--stream-data=preserve', '--object-streams=preserve', '--normalize-content=n', '--newline-before-endstream', '--linearize', '/var/tmp/djpdf-1p_vtodx/temp.pdf', '/home/user/scans2.pdf']

[DiagonalArg]

Symlinking jbig2 to jbig2enc, also produces errors:

$ scans2pdf -v Feigon-001-000.crop_2R.tif scans2.pdf
DEBUG:Using selector: EpollSelector
DEBUG:Running command: ['convert', '-colorspace', 'sRGB', '-profile', '/home/dev/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/argyllcms-srgb.icm', '-background', '#ffffff', '-alpha', 'remove', '-alpha', 'off', '-type', 'TrueColor', '/home/user/Lee.finished/Feigon-Images/out/Feigon-001-000.crop_2R.tif', '/var/tmp/djpdf-kb6b1v1n/image.png']
DEBUG:convert-im6.q16: profile 'icc': 'RGB ': RGB color space not permitted on grayscale PNG `/var/tmp/djpdf-kb6b1v1n/image.png' @ warning/png.c/MagickPNGWarningHandler/1668.

DEBUG:Running command: ['convert', '-fill', '#000000', '-opaque', '#000000', '-fill', '#000000', '-opaque', '#000000', '-threshold', '0', '/var/tmp/djpdf-kb6b1v1n/image.png', '/var/tmp/djpdf-3yk3pn39/image.png']
DEBUG:Running command: ['identify', '-units', 'PixelsPerInch', '-format', '%x %y', '/var/tmp/djpdf-kb6b1v1n/image.png']
DEBUG:Running command: ['convert', '-fill', '#ffffff', '-opaque', '#000000', '-resize', '50%', '/var/tmp/djpdf-kb6b1v1n/image.png', '/var/tmp/djpdf-ftx7rfk1/image.png']
DEBUG:Running command: ['identify', '-format', '%w %h', '/var/tmp/djpdf-kb6b1v1n/image.png']
DEBUG:Running command: ['convert', '-format', '%c', '/var/tmp/djpdf-3yk3pn39/image.png', 'histogram:info:-']
DEBUG:Running command: ['convert', '-format', '%c', '/var/tmp/djpdf-ftx7rfk1/image.png', 'histogram:info:-']
DEBUG:Running command: ['convert', '-fill', '#000000', '-opaque', '#000000', '-fill', '#000000', '-opaque', '#000000', '-threshold', '0', '/var/tmp/djpdf-kb6b1v1n/image.png', '/var/tmp/djpdf-amjl3335/image.png']
DEBUG:Running command: ['tesseract', '-l', 'eng', '--dpi', '600', '/var/tmp/djpdf-amjl3335/image.png', '/var/tmp/djpdf-9ap6ewya/ocr', 'hocr']
DEBUG:Tesseract Open Source OCR Engine v4.1.1 with Leptonica

INFO:Can't extract textangle from ocr_line: bbox 716 941 826 987; baseline 0 0; x_size 61; x_descenders 15.25; x_ascenders 15.25
DEBUG:Exception occurred:
Traceback (most recent call last):
  File "/home/dev/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/hocr.py", line 46, in extract_text
    textangle = textangle_regex.search(line.attrib["title"]).group(1)
AttributeError: 'NoneType' object has no attribute 'group'

INFO:Can't extract textangle from ocr_line: bbox 643 1005 898 1043; baseline -0.008 -6; x_size 37; x_descenders 7; x_ascenders 8
DEBUG:Exception occurred:
Traceback (most recent call last):
  File "/home/dev/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/hocr.py", line 46, in extract_text
    textangle = textangle_regex.search(line.attrib["title"]).group(1)
AttributeError: 'NoneType' object has no attribute 'group'

WARNING:Lossy JBIG2 compression can alter text in a way that is not noticeable as corruption (e.g. the numbers '6' and '8' get replaced)
DEBUG:Running command: ['convert', '-alpha', 'remove', '-alpha', 'off', '-colorspace', 'gray', '-threshold', '50%', '/var/tmp/djpdf-3yk3pn39/image.png', '/var/tmp/djpdf-lykzi68v/input.0.png']
DEBUG:Running command: ['jbig2', '-p', '-s', '-t', '0.9', '/var/tmp/djpdf-lykzi68v/input.0.png']
DEBUG:Error in fopenReadStream: file not found
Unable to open "/var/tmp/djpdf-lykzi68v/input.0.png"

ERROR:Command '['jbig2', '-p', '-s', '-t', '0.9', '/var/tmp/djpdf-lykzi68v/input.0.png']' returned non-zero exit status 1
DEBUG:Exception occurred:
Traceback (most recent call last):
  File "/home/dev/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/scans2pdfcli.py", line 392, in main
    asyncio.run(build_pdf(pages, out_file))
  File "/usr/lib/python3.10/asyncio/runners.py", line 44, in run
    return loop.run_until_complete(main)
  File "/usr/lib/python3.10/asyncio/base_events.py", line 646, in run_until_complete
    return future.result()
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/scans2pdf.py", line 589, in build_pdf
    return await pdf_builder.write(
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/djpdf.py", line 867, in write
    await asyncio.gather(
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/djpdf.py", line 734, in make_page
    await asyncio.gather(
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/djpdf.py", line 576, in pdf_image
    return await self._image.pdf_image(psem)
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/djpdf.py", line 433, in pdf_image
    return await self._cache.get(self._pdf_image(psem))
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/util.py", line 121, in get
    self._content = await content_future
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/djpdf.py", line 514, in _pdf_image
    (jbig2_images, jbig2_globals), image_masks = await asyncio.gather(
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/djpdf.py", line 496, in get_jbig2_images
    await run_command(cmd, psem, cwd=temp_dir)
  File "/home/user/.local/pipx/venvs/djpdf/lib/python3.10/site-packages/djpdf/util.py", line 169, in run_command
    raise CalledProcessError(proc.returncode, args, None)
subprocess.CalledProcessError: Command '['jbig2', '-p', '-s', '-t', '0.9', '/var/tmp/djpdf-lykzi68v/input.0.png']' returned non-zero exit status 1.

CRITICAL:Operation failed

$ jbig2 -p -s -t 0.9 ~/Constitution.png 
JBIG2 compression complete. pages:1 symbols:127 log2:7
$ echo $?
0

[Unrud]

Unable to open "/var/tmp/djpdf-lykzi68v/input.0.png"

Temporary files are stored in /var/tmp/. My guess is that Snap jbig2 doesn't have access to this folder on the host or some similar issue related to sandboxing.