The main server software used for MCPE servers is Pocketmine-MP, which works and it's okay for the most part but it is heavily underpowered and there are many alternatives better than it, for instance:
Altay
Altay, a spoon of Pocketmine, it runs the same as Pocketmine but has much more support, you can swim here which is a feature not present in Pocketmine yet, netherite and more item support. It is compatible with every Pocketmine plugin so nothing else needs to be added for it. Elytra support. Much more implemented features that Pocketmine is lacking in, and it is fairly easy to implement, all you have to do is replace the Pocketmine-MP.phar file with an Altay.phar file renamed to Pocketmine-MP.phar to replace it. A download to it is here, scroll down to the Jenkins file and tap download build and there it is. There are videos that are really helpful on it to such as this.
Nukkit
Completely different from Pocketmine-MP, it runs on java instead of pmmp. It hasn't been officially updated to 1.16.2 yet but there is a development build here, it works but it is a little laggy since yeah it's still a development branch build. All plugins for it are here. Nukkit has more blocks than what is present in Pocketmine and more than what is in Altay, the community there is actually much more supportive and rampant than the one present for Pocketmine and is a much better alternative. The branch for it officialy is this one. Nukkit. Between both I'd really appreciate if this one were added more but Altay has the same plugin support as Pocketmine and it's understandable.
There are many more server softwares for mcpe but these are the ones compatible with 1.16.2 at the moment, the rest are still on 1.16.1. Thank you for reading 