Oddly enough I was chatting to @harshil1712 about this the other day. In my testing I found that you can map your OS font folder to the docker container by adding the below to the volumes.
If you install the fonts on your server or pop them in a folder somewhere you can just map it to the container path of /usr/share/fonts/truetype/host and give the container a bounce and they should appear.
I met the same problem, my n8n running in docker & do not support edit docker-compose file. I think maybe I can write I bash file & run it everyday to sync my font to n8n🤔