Joplin Hotfolder plug-in stopped working

The Joplin Hotfolder plug-in stopped working on my LMDE 5 system. The solution was to add fs.file-max = 4096000 to /etc/sysctl.conf.

fs.file-max sets the maximum number of file-handles that the Linux kernel will allocate. The rule of thumb is 64000 for every 1 GB of RAM.