root@wiki:~/wiki# node server
Loading configuration from /root/wiki/config.yml... OK
2021-09-12T15:33:04.015Z [MASTER] info: =======================================
2021-09-12T15:33:04.016Z [MASTER] info: = Wiki.js 2.5.214 =====================
2021-09-12T15:33:04.016Z [MASTER] info: =======================================
2021-09-12T15:33:04.017Z [MASTER] info: Initializing...
2021-09-12T15:33:04.378Z [MASTER] info: Using database driver pg for postgres [ OK ]
2021-09-12T15:33:04.381Z [MASTER] info: Connecting to database...
2021-09-12T15:33:04.400Z [MASTER] info: Database Connection Successful [ OK ]
2021-09-12T15:33:04.700Z [MASTER] warn: Mail is not setup! Please set the configuration in the administration area!
2021-09-12T15:33:04.755Z [MASTER] info: Loading GraphQL Schema...
2021-09-12T15:33:05.125Z [MASTER] error: globalThis is not defined

Fix it by installing/updating a more recent version of node.js, for example, I have installed the LTS version, and fixed the error for myself:

# Using Ubuntu, as root
curl -fsSL https://deb.nodesource.com/setup_lts.x | sudo -E bash -
apt-get install -y nodejs

# Using Debian, as root
curl -fsSL https://deb.nodesource.com/setup_16.x | bash -
apt-get install -y nodejs

source