I'd really like to update my small private server to 1.13.2, but somehow there seem to be some changes, that won't allow me to do so. Important side note: I have no problems starting the 1.13.1 server JAR!!
The same crash happens with the recent 18w43b server JAR, even with a clean folder. Since the whole JAR crashes, before "Minecraft" even has a chance to start, there is no log file (folder is empty).
However, here is my screen output (user and server URL have been removed due to privacy/security).
user@xxx:~/1.13.2$ java -Xms1G -Xmx3G -jar server.jar nogui
Exception in thread "main" java.lang.OutOfMemoryError: unable to create new native thread
at java.lang.Thread.start0(Native Method)
user@xxx:~/1.13.2$ free -m
total used free shared buffers cached
Mem: 4096 651 3444 0 0 355
-/+ buffers/cache: 295 3800
Swap: 0 0 0
user@xxx:~/1.13.2$ lsb_release -a
No LSB modules are available.
Distributor ID: Ubuntu
Description: Ubuntu 12.04.5 LTS
user@xxx:~/1.13.2$ java -version
openjdk version "1.8.0_111"
OpenJDK Runtime Environment (build 1.8.0_111-8u111-b14-3~12.04-b14)
OpenJDK 64-Bit Server VM (build 25.111-b14, mixed mode)
As seen, there is more than 3GB RAM free for usage, but the server file still seem to think, that there's not enough RAM. Did you change the minimal requirements?