Minecraft: Bedrock Edition just got an update that we recently detailed, but there's one notable element missing from the Switch version. For whatever reason, the Switch update doesn't include support for dedicated servers. This is confirmed by a Mojang FAQ.
Anyone playing on the bedrock editions will be able to connect to the server, with the current exception of Nintendo Switch users.
We don't have any idea why this feature wasn't included, nor do we have info on whether it will be implemented in a future update.