docs: update docs, remove problematic flag from Dockerfile

apps/extension/FIREFOX_README.md

@@ -14,7 +14,7 @@ exactly as they are described below.
 
 **NOTE** The add-on submission was built in the following environment:
 
-- Ubuntu Server 24.04 LTS **x86_64** - Please ensure your environment matches this to produce an identical build!
+- Ubuntu Desktop 24.04 LTS **AMD64** - Please ensure your environment matches this to produce an identical build!
 - Docker version 27.x
 
 Follow these instructions to build with Docker:
@@ -47,6 +47,50 @@ docker run --rm -v ./apps/extension/build:/shared namada-keychain-firefox cp -r
 
 If Docker is not currently installed in your environment, please refer to the [instructions of the official Docker documentation](https://docs.docker.com/engine/install/ubuntu/).
 
+The steps we took to install Docker on Ubuntu Desktop 24.04 ARM64 are as follows:
+
+1. Remove any pre-existing Docker-related packages:
+
+```bash
+for pkg in docker.io docker-doc docker-compose docker-compose-v2 podman-docker containerd runc; do sudo apt-get remove $pkg; done
+```
+
+2. Setup Docker repository and install keyring
+
+```bash
+# Add Docker's official GPG key:
+sudo apt-get update
+sudo apt-get install ca-certificates curl
+sudo install -m 0755 -d /etc/apt/keyrings
+sudo curl -fsSL https://download.docker.com/linux/ubuntu/gpg -o /etc/apt/keyrings/docker.asc
+sudo chmod a+r /etc/apt/keyrings/docker.asc
+
+# Add the repository to Apt sources:
+echo \
+  "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.asc] https://download.docker.com/linux/ubuntu \
+  $(. /etc/os-release && echo "$VERSION_CODENAME") stable" | \
+  sudo tee /etc/apt/sources.list.d/docker.list > /dev/null
+sudo apt-get update
+```
+
+3. Install Docker packages:
+
+```bash
+sudo apt-get install docker-ce docker-ce-cli containerd.io docker-buildx-plugin docker-compose-plugin
+```
+
+4. Post-install - Add `docker` group to user:
+
+```bash
+# If docker group doesn't currently exist:
+sudo groupadd docker
+
+# Add current user to docker group:
+sudo usermod -aG docker $USER
+```
+
+5. Log out, then log back in for group to take effect! This is to ensure that you don't need to run our Docker commands as root via `sudo`.
+
 [ [Table of Contents](#table-of-contents) ]
 
 ### Source code

docker/extension/Dockerfile

@@ -1,4 +1,4 @@
-FROM --platform=linux/amd64 rust:1.79 AS builder
+FROM rust:1.79 AS builder
 
 WORKDIR /app