Adding SuperHTML support to BBEdit only requires tweaking the existing settings for HTML language support. Existing support uses the vscode-html-languageserver, which is a NodeJS project. You can easily change that to SuperHTML by doing the following:

Accessing the HTML language settings

• Open the BBEdit preferences by accessing the “BBEdit” menu and then choose “Settings” (or via the keyboard ⌘+, shortcuts).
• From the settings window navigate to the “Languages” tab.
• In this tab, choose the “Custom Settings” tab.
• If you already have a custom configuration, you may edit it now. However, if you don’t have an item listed for HTML, click on the “+” dropdown and choose “HTML” from the list.
• In this new sheet window, select the “Server” tab, clearing out the existing html-languageserver and —stdio boxes and filling in superhtml in the “Command” text box, and “lsp” in the “Arguments” box.
• Once you’ve entered both of those items, you should see a green checkmark indicating that the server is ready to be used.
• Click on “OK” and your settings will be applied. You should be able to open an HTML document, or create a new one, and SuperHTML will be used as the LSP for checking for errors and warnings.