How to get three displays on Linux Mint 21

This is a follow-up on [How to get 3 monitors working in Linux Mint 18](https://unix.stackexchange.com/questions/311798/how-to-get-3-monitors-working-in-linux-mint-18) . I am on a Dell Laptop with one HDMI output, but the cables are plugged in on a dock. I highly doubt that the laptop brand/type/version plays any role since anyone has the problem *(unless they have two graphic cards in a desktop pc perhaps?)*. I cannot add more than one other monitor to my Linux Mint 21, plugged in at the laptop, which has just one graphical output. Even on Ubuntu, there is just the official [DisplayLink USB Graphics Software for Ubuntu](https://www.synaptics.com/products/displaylink-graphics/downloads/ubuntu) for 20.04 and 22.04, but not for 21.04, though for Ubuntu, there was a fix for this to update the firmware on the dock, see [Ubuntu 21.04 displaylink not working - DisplayLink Forum](https://www.displaylink.org/forum/showthread.php?t=67714) , taken from [Ubuntu 21.04 with three external monitors - Ask Ubuntu](https://askubuntu.com/a/1350597/1110856) . And that would not even work since it is needed for Linux Mint, which only builds on Ubuntu, but needs its own driver for the screens. For Linux Mint, I found much the same problems for earlier versions, like [Setting up multiple screens. - Linux Mint Forums](https://forums.linuxmint.com/viewtopic.php?t=287087) . *(needless to say, but for anyone of you testing this, you need to restart your machine after any DisplayLink driver change)* How to get three screens/displays/monitors on Linux Mint 21?