I've messed about with SMB1, FTP and Webdav. I can get FTP mapped in windows 11 but read only. I can get http/webdav working okay in firefox. But i'd really like to browse the phone like a network drive where I can read/write inside the file manager. Is this possible. I've checked the FAQ but i'm fairly new to this all.
You can do that but it would help if you could make your description more specific. As FTP is robust and supported natively by most OS, and was the basis for the FAQ let's use FTP for now. Please correct this if inaccurate but what I get from your description is: that you are running the MiXplorer (FTP) server on an Android device and attempting to access it across a LAN from a Windows 11 device and in Firefox or the native file explorer (or an FTP client).
If that is correct, then I would recommend configuring and testing with a dedicated FTP client such as Filezilla on the PC. Even though the Windows Explorer UI makes the experience seamless after there is a good connection, the Windows connections are notoriously difficult to reconfigure as they offer no simple interface for configuring the connection parameters and tend to attempt previous bad connections - just what you don't want when testing connections in sequence with various parameters. In addition to the syntax of the URL of the server and the port number there are other parameters in the server settings which which must match the client. Filezilla allows you to configure the connection parameters in detail and save or copy them as profiles, and provides good logging. Once the FTP access is working via Filezilla then it's much easier to configure Windows Explorer for direct access.
See sections "General Server Settings: " and "Account settings." and "Home Path" in the FAQ servers post: https://forum.xda-developers.com/t/mixplorer-q-a-and-faq-user-manual.3308582/post-65157350
If you have questions along the way I (and probably others) would be glad to help in the FAQ thread (unless this becomes a bug rather than a configuration issue in which case it should come back here). As this discussion could sprawl into configuration aspects of Windows, Android, networking and MiXplorer it would be better to bring it to the FAQ as long as it seems to be a configuration issue.