I changed the server.js file a bit as sunnyson suggested:
module.exports = ({ env }) => ({
host: env('HOST', '0.0.0.0'),
port: env.int('PORT', 1337),
url: 'http://167.99.243.1/api',
admin: {
url: '/dashboard',
secret: 'krr/BQpkW18rZB+kjULCJVt7qI2E1Cop6JvQINxRwZD4N9kIL0QLufaa8VUzPror/QWQsxxJWsBjEYp9wp9zRw=='
},
});
Also I hardcoded the JWT secret value.
Cleared the .cache and build folders, rebuilt with yarn build, but no luck I got the same secretOrPrivateKey error after the login attempt.