I apologize for not responding sooner here. We were running an outdated Bedrock version for a couple days before anyone noticed. Beta builds aren't supported on Minetown, only full release builds.
Regarding linking an account, it is not mandatory. You can play on either a Java or Bedrock account, or both (As long as it's not at the same time). Unlinked accounts are distinguished by a * before their name.
You can unlink an account at any time in the server with /unlinkaccount. I'm not sure what it will look like when Java and Microsoft accounts are combined.