Setting up an older Metamask to support eip1559 with Trezor

gistfile1.txt

Problem: While using Metamask with your Trezor you get “replacement fee too low” or other error when doing transactions on some Web3 sites. This is because the MM update to support Trezor with eip1559 is not out yet.

Metamask Chrome versions:
- MetaMask Version 9.8.4 (old version that works with Trezor + MM + EIP-1559)
- MetaMask Version 10.2.0 (latest)

To install old version of Metamask:
1. First make sure you are running the latest Trezor firmware. At the time of this writing it's core/v2.4.2 from Aug 27.
2. Next you should do this in a new Chrome profile (Chrome > Profile > Add Profile) if you don't want to kill your existing Metamask. Chrome is actually able to run both copies of Metamask but I find many web3 sites will error if you try to keep both. By creating a new Chrome profile you can just have the old Metamask there. 
3. Download the old version directly from the Github source only: https://github.com/MetaMask/metamask-extension/releases/tag/v9.8.4
4. Unzip the folder of files to your Desktop
5. In your new Chrome profile visit chrome://extensions/ and check the box for Developer mode in the top right.
6. Click the "Load unpacked extension" button and select the unzipped folder for your extension to install it.
7. Import an existing MM wallet or create a new one. It's only needed so you can start importing your actual hardware wallet account(s) afterwards.
8. Done! Transactions should work now on Web3 sites until MM has the latest fix out!

This worked for me. No guarantees it works for everyone else and on all Web3 sites. This is my hardware used:
- Macbook Pro 
- Chrome Version 94.0.4606.71 (Official Build) (x86_64)
- Trezor Model T (firmware core/v2.4.2 latest from Aug 27)

Special thanks to the following sources:
- https://www.reddit.com/r/TREZOR/comments/pbfumi/eip1559/
- https://www.cnet.com/tech/services-and-software/how-to-install-chrome-extensions-manually/