Fix certbot/cerbot image pulling for ARM32 and ARM64

Related to #529 (Github Issue).

docs/alternative-architectures.md

@@ -1,22 +1,27 @@
 # Alternative architectures
+
 As stated in the [Prerequisites](prerequisites.md), currently only x86_64 is supported. However, it is possible to set the target architecture, and some tools can be built on the host or other measures can be used.
 
 To that end add the following variable to your `vars.yaml` file:
-```
+
+```yaml
 matrix_architecture: <your-matrix-server-architecture>
 ```
+
 Currently supported architectures are the following:
 - `amd64` (the default)
 - `arm64`
 - `arm32`
 
-so for the Raspberry Pi the following should be in your `vars.yaml` file:
-```
+so for the Raspberry Pi, the following should be in your `vars.yaml` file:
+
+```yaml
 matrix_architecture: "arm32"
 ```
 
 ## Implementation details
-This subsection is used for a reminder, how the different roles implement architecture differenes. This is **not** aimed at the users, so one does not have to do anything based on this subsection.
+
+This subsection is used for a reminder, how the different roles implement architecture differences. This is **not** aimed at the users, so one does not have to do anything based on this subsection.
 
 On most roles [self-building](self-building.md) is used if the architecture is not `amd64`, however there are some special cases:
 - `matrix-bridge-mautrix-facebook`: there is a pre-built Docker image for `arm64` as well

group_vars/matrix_servers

@@ -675,7 +675,13 @@ matrix_ssl_domains_to_obtain_certificates_for: |
     ([matrix_domain] if matrix_nginx_proxy_base_domain_serving_enabled else [])
   }}
 
-matrix_ssl_architecture: "{{ matrix_architecture }}"
+matrix_ssl_architecture: "{{
+	{
+		'amd64': 'amd64',
+		'arm32': 'arm32v6',
+		'arm64': 'arm64v8',
+	}[matrix_architecture]
+}}"
 
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 #