Yes, this is still present in 20.04 with printer-driver-cups-pdf 3.0.1-6, limited to original reporter’s case of having the symlink point to another filesystem; if I point ~/PDF to, say ~/tmp/PDF (without crossing filesystem borders), the PDF is created without issue, whereas having ~/PDF linked to /media/$USER/$USB_THUMBDRIVE/PDF/ does still cause it to fail:

[…]
Sat Dec 26 16:48:07 2020 [DEBUG] output filename created: /home/jani/PDF/Bug__1092099__342_200_234inconsistent_behavior_for…ry_342_200_-job_8.pdf
Sat Dec 26 16:48:07 2020 [DEBUG] ghostscript commandline built: /usr/bin/gs -q -dCompatibilityLevel=1.2 -dNOPAUSE -dBATCH -dSAFER -sDEVICE=pdfwrite -sOutputFile=”/home/jani/PDF/Bug__1092099__342_200_234inconsistent_behavior_for…ry_342_200_-job_8.pdf” -dAutoRotatePages=/PageByPage -dAutoFilterColorImages=false -dColorImageFilter=/FlateEncode -dPDFSETTINGS=/prepress -c .setpdfwrite -f /var/spool/cups-pdf/SPOOL/cups2pdf-233705
Sat Dec 26 16:48:07 2020 [DEBUG] output file unlinked: /home/jani/PDF/Bug__1092099__342_200_234inconsistent_behavior_for…ry_342_200_-job_8.pdf
Sat Dec 26 16:48:07 2020 [DEBUG] TMPDIR set for GhostScript: /var/tmp
Sat Dec 26 16:48:07 2020 [DEBUG] waiting for child to exit
Sat Dec 26 16:48:07 2020 [DEBUG] entering child process
Sat Dec 26 16:48:07 2020 [DEBUG] GID set for current user
Sat Dec 26 16:48:07 2020 [DEBUG] supplementary groups set for current user
Sat Dec 26 16:48:07 2020 [DEBUG] UID set for current user: jani
Sat Dec 26 16:48:07 2020 [DEBUG] ghostscript has finished: 256
Sat Dec 26 16:48:07 2020 [ERROR] failed to set file mode for PDF file: /home/jani/PDF/Bug__1092099__342_200_234inconsistent_behavior_for…ry_342_200_-job_8.pdf (non fatal)
Sat Dec 26 16:48:07 2020 [DEBUG] ERRNO: 2 (No such file or directory)
Sat Dec 26 16:48:07 2020 [DEBUG] no postprocessing
Sat Dec 26 16:48:07 2020 [DEBUG] spoolfile unlinked: /var/spool/cups-pdf/SPOOL/cups2pdf-233705
Sat Dec 26 16:48:07 2020 [DEBUG] all memory has been freed
Sat Dec 26 16:48:07 2020 [STATUS] PDF creation successfully finished for jani
jani@latimeria:~$ ls -l PDF
lrwxrwxrwx 1 jani jani 27 joulu 26 16:47 PDF -> /media/jani/KINGSTON_1G/PDF
jani@latimeria:~$ ls -l PDF/
yhteensä 0