Recently upgraded to 19.04 and since then cannot print custom format cheques on GNUcash

For diagnostic purposes try the following:

Open a teminal window (e.g. by simultaneously pressing ctrl-alt-t) and start gnucash by issuing the command

gnucash

Does this provide useful information when the program crashes?

Here is the output:
john@john-H81M-S2H-GSM:~$ gnucash
Found Finance::Quote version 1.47
! SyncTeX Error : No file?
Segmentation fault (core dumped)
john@john-H81M-S2H-GSM:~$

Thank you for your help

This does not help.
Try again with the command

strace gnucash

and after the crash copy/paste the last page of messages (there will probably be very much output, so please limit it to the last page for the time being).

Hi,
The problem seems to be related to a template CCCU and not my other custom template Coastal
Here is the end of the output with CCCU:
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=4, events=POLLIN}, {fd=5, events=POLLIN}, {fd=6, events=POLLIN}], 3, 288) = 1 ([{fd=4, revents=POLLIN}])
recvmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\241 \340\25\3\0`\2\323\1\0\0\220\1\0\0\0\0\0\0\2342\0\0\33A\0\0\320\7\0\0"..., iov_len=4096}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 64
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=4, events=POLLIN}, {fd=5, events=POLLIN}, {fd=6, events=POLLIN}], 3, 275) = 1 ([{fd=4, revents=POLLIN}])
recvmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\241 \340\25\3\0`\2\322\1\0\0\222\1\0\0\0\0\0\0x\264l\17\17\0\0\0\0\0\0\0", iov_len=4096}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 32
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=4, events=POLLIN}, {fd=5, events=POLLIN}, {fd=6, events=POLLIN}], 3, 0) = 0 (Timeout)
poll([{fd=4, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
writev(4, [{iov_base="5\30\4\0\363\4`\2\3\0`\2\226\0\17\0\213\4\6\0\364\4`\2\363\4`\2*\0\0\0"..., iov_len=860}, {iov_base=NULL, iov_len=0}, {iov_base="", iov_len=0}], 3) = 860
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=4, events=POLLIN}, {fd=5, events=POLLIN}, {fd=6, events=POLLIN}], 3, 271) = 1 ([{fd=4, revents=POLLIN}])
recvmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="#\203\353\25\26\0\0\0\5\0\2\0\36\375\332\3\1\0\0\0\n\1\0\0>\1`\2\0\0\0\0"..., iov_len=4096}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 120
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=4, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
writev(4, [{iov_base="$\30\1\0\203(\3\0\n\1\0\0\2\0\17\0", iov_len=16}, {iov_base=NULL, iov_len=0}, {iov_base="", iov_len=0}], 3) = 16
poll([{fd=4, events=POLLIN}], 1, -1) = 1 ([{fd=4, revents=POLLIN}])
recvmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\1(\355\25\7\0\0\0\n\1\0\0>\1`\2\0\0\262\4\0\0y\2\0\0\262\4\0\0y\2"..., iov_len=4096}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 60
poll([{fd=4, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
writev(4, [{iov_base="\203(\3\0>\1`\2\2\0\0\0", iov_len=12}, {iov_base=NULL, iov_len=0}, {iov_base="", iov_len=0}], 3) = 12
poll([{fd=4, events=POLLIN}], 1, -1) = 1 ([{fd=4, revents=POLLIN}])
recvmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\1(\356\25\7\0\0\0\n\1\0\0\0\0\0\0\0\0\262\4\0\0y\2\0\0)\2\0\0\320\0"..., iov_len=4096}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 60
poll([{fd=4, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
writev(4, [{iov_base="%(\1\0", iov_len=4}, {iov_base=NULL, iov_len=0}, {iov_base="", iov_len=0}], 3) = 4
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
recvmsg(4, {msg_namelen=0}, 0) = -1 EAGAIN (Resource temporarily unavailable)
poll([{fd=4, events=POLLIN|POLLOUT}], 1, -1) = 1 ([{fd=4, revents=POLLOUT}])
writev(4, [{iov_base="+(\1\0", iov_len=4}, {iov_base=NULL, iov_len=0}, {iov_base="", iov_len=0}], 3) = 4
poll([{fd=4, events=POLLIN}], 1, -1) = 1 ([{fd=4, revents=POLLIN}])
recvmsg(4, {msg_name=NULL, msg_namelen=0, msg_iov=[{iov_base="\1\2\360\25\0\0\0\0?\1`\2\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0\0", iov_len=4096}], msg_iovlen=1, msg_controllen=0, msg_flags=0}, 0) = 32
write(5, "\1\0\0\0\0\0\0\0", 8) = 8
futex(0x55c196ac9310, FUTEX_WAKE_PRIVATE, 2147483647) = 0
write(5, "\1\0\0\0\0\0\0\0", 8) = 8
openat(AT_FDCWD, "/home/john/.local/share/gnucash/expressions-2.0", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 24
write(24, "", 0) = 0
close(24) = 0
openat(AT_FDCWD, "/home/john/.local/share/gnucash/stylesheets-2.0", O_WRONLY|O_CREAT|O_TRUNC, 0666) = 24
fcntl(24, F_GETFL) = 0x8001 (flags O_WRONLY|O_LARGEFILE)
fstat(24, {st_mode=S_IFREG|0644, st_size=0, ...}) = 0
lseek(24, 0, SEEK_CUR) = 0
write(24, "(let ((template (gnc:html-style-"..., 1614) = 1614
close(24) = 0
close(3) = 0
getpid() = 18919
getpid() = 18919
exit_group(0) = ?
+++ exited with 0 +++
john@john-H81M-S2H-GSM:~$

What is the output of:

lsb_release -a; uname -a; apt-cache policy gnucash

Thanks

john@john-H81M-S2H-GSM:~$ lsb_release -a; uname -a; apt-cache policy gnucash
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 19.04
Release: 19.04
Codename: disco
Linux john-H81M-S2H-GSM 5.3.0-26-generic #28~18.04.1-Ubuntu SMP Wed Dec 18 16:40:14 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
gnucash:
  Installed: 1:3.4-1
  Candidate: 1:3.4-1
  Version table:
 *** 1:3.4-1 500
        500 http://archive.ubuntu.com/ubuntu disco/universe amd64 Packages
        100 /var/lib/dpkg/status
john@john-H81M-S2H-GSM:~$

Thank you as always

Thanks actionparsnip, that solved my question.