Файла нет, при том ни если попробовать png на выход такая же история. Если попробовать этот же пример на plantuml.com то диаграмма создается. Если локально попробовать не json пример то файл тоже создается.
~/Downloads/UML$ strace plantuml -tpng -progress -duration example.json
execve("/usr/bin/plantuml", ["plantuml", "-tpng", "-progress", "-duration", "example.json"], 0x7ffe9f33dff0 /* 47 vars */) = 0
brk(NULL) = 0x562bc465c000
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
access("/etc/ld.so.preload", R_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/etc/ld.so.cache", O_RDONLY|O_CLOEXEC) = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=198182, ...}) = 0
mmap(NULL, 198182, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7fcdfe8be000
close(3) = 0
access("/etc/ld.so.nohwcap", F_OK) = -1 ENOENT (No such file or directory)
openat(AT_FDCWD, "/lib/x86_64-linux-gnu/libc.so.6", O_RDONLY|O_CLOEXEC) = 3
read(3, "\177ELF\2\1\1\3\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\20\35\2\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=2030928, ...}) = 0
mmap(NULL, 8192, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7fcdfe8bc000
mmap(NULL, 4131552, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7fcdfe2d5000
mprotect(0x7fcdfe4bc000, 2097152, PROT_NONE) = 0
mmap(0x7fcdfe6bc000, 24576, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x1e7000) = 0x7fcdfe6bc000
mmap(0x7fcdfe6c2000, 15072, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7fcdfe6c2000
close(3) = 0
arch_prctl(ARCH_SET_FS, 0x7fcdfe8bd540) = 0
mprotect(0x7fcdfe6bc000, 16384, PROT_READ) = 0
mprotect(0x562bc2e0c000, 8192, PROT_READ) = 0
mprotect(0x7fcdfe8ef000, 4096, PROT_READ) = 0
munmap(0x7fcdfe8be000, 198182) = 0
getuid() = 1001
getgid() = 1001
getpid() = 9540
rt_sigaction(SIGCHLD, {sa_handler=0x562bc2c03200, sa_mask=~[RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7fcdfe314040}, NULL, 8) = 0
geteuid() = 1001
brk(NULL) = 0x562bc465c000
brk(0x562bc467d000) = 0x562bc467d000
getppid() = 9538
stat("/mnt/DATA1TB/Downloads/UML", {st_mode=S_IFDIR|0775, st_size=48, ...}) = 0
stat(".", {st_mode=S_IFDIR|0775, st_size=48, ...}) = 0
openat(AT_FDCWD, "/usr/bin/plantuml", O_RDONLY) = 3
fcntl(3, F_DUPFD, 10) = 10
close(3) = 0
fcntl(10, F_SETFD, FD_CLOEXEC) = 0
geteuid() = 1001
getegid() = 1001
rt_sigaction(SIGINT, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0
rt_sigaction(SIGINT, {sa_handler=0x562bc2c03200, sa_mask=~[RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7fcdfe314040}, NULL, 8) = 0
rt_sigaction(SIGQUIT, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0
rt_sigaction(SIGQUIT, {sa_handler=SIG_DFL, sa_mask=~[RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7fcdfe314040}, NULL, 8) = 0
rt_sigaction(SIGTERM, NULL, {sa_handler=SIG_DFL, sa_mask=[], sa_flags=0}, 8) = 0
rt_sigaction(SIGTERM, {sa_handler=SIG_DFL, sa_mask=~[RTMIN RT_1], sa_flags=SA_RESTORER, sa_restorer=0x7fcdfe314040}, NULL, 8) = 0
read(10, "#!/bin/sh\n# PlantUML Launcher\n#\n"..., 8192) = 1051
geteuid() = 1001
faccessat(AT_FDCWD, "/usr/bin/java", X_OK) = 0
clone(child_stack=NULL, flags=CLONE_CHILD_CLEARTID|CLONE_CHILD_SETTID|SIGCHLD, child_tidptr=0x7fcdfe8bd810) = 9541
wait4(-1, Duration = 0.262 seconds
[{WIFEXITED(s) && WEXITSTATUS(s) == 0}], 0, NULL) = 9541
--- SIGCHLD {si_signo=SIGCHLD, si_code=CLD_EXITED, si_pid=9541, si_uid=1001, si_status=0, si_utime=71, si_stime=7} ---
rt_sigreturn({mask=[]}) = 9541
read(10, "", 8192) = 0
exit_group(0) = ?
+++ exited with 0 +++