Please note that the directions below were written up for Fedora users and were tested on Fedora 30. The directions will be identical on at least some distributions and releases other than Fedora. For other distributions you may need to use a different command to discover IP information or set a static IP address.
To reload the firmware on a ThinkPenguin TPE-R1100, you will need a computer with the necessary software and an Ethernet port, plus an Ethernet cable to connect the computer to the TPE-R1100.
Load an image of the TPE-R1100 firmware onto the computer. You can find a suitable image file on the CD that came with your TPE-R1100. It is in the bin directory, named librecmc-ar71xx-generic-tpe-r1100-squashfs-sysupgrade.bin.
Power down the TPE-R1100 and disconnect it from your network. Disconnect the computer from your network. Reconfigure its network software so it will communicate with the TPE-R1100 in point-to-point mode, as follows:
sudo systemctl stop NetworkManager
sudo ifconfig enp1s0 pointopoint 192.168.1.1
sudo ifconfig enp1s0 192.168.1.2
The above three commands are for Fedora 30. If you are using a different distribution of GNU/Linux your commands may be different. The first line disables the Network Manager. The second sets Ethernet interface enp1s0 to point-to-point mode, with the IPv4 address 192.168.1.1 at the other end. Note the peculiar spelling of the pointopoint keyword; I expected it to be spelled pointtopoint. The third line specifies the IPv4 address of your Ethernet interface. On my computer the only Ethernet interface is named enp1s0; yours may be different. To see a list of your Ethernet interfaces type ifconfig with no arguments.
Connect your Ethernet cable between the Ethernet interface on your computer and the Ethernet interface marked LAN on the TPE-R1100.
On the left side of the TPE-R1100 you will find a button marked Reset. Hold it down while you apply power to the TPE-R1100. Wait for the three LEDs on the front of the TPE-R1100 to blink four times, then release the Reset button. The three LEDs will cycle slowly from bright to dim and back again. This is telling you that the device is in bootstrap mode.
Start a web browser, telling it to connect to the TPE-R1100 over the Ethernet cable:
firefox 192.168.1.1
The web browser will bring up a bootstrap page which invites you to select a suitable image. Choose the image file you obtained above, whose name ends in sysupgrade.bin. Tell the page to write that data into the router's flash memory.
The flashing process will take more than a minute. When it is done you can restart both your computer and the TPE-R1100 router. Since the router is now functional, though with its default configuration and no access to the internet, it will assign an IPv4 address to your computer. It will probably be of the form 192.168.10.<number>, where <number> is between 100 and 150. The router itself will have the address 192.168.10.1. You can now run a browser to configure the TPE-R1100:
firefox 192.168.10.1
You should configure the router before connecting it to the internet. In particular, you should set the password and not permit SSH access to the TPE-R1100 from the internet.
Once the router is configured to your satisfaction you can use another Ethernet cable to connect the WAN port of the TPE-R1100 to your internet modem. Don't forget to save the router's configuration on your computer. If you have to do this again, you can load the saved configuration after flashing the TPE-R1100.