AnyVersion is a plugin that allows your players to play with older clients. This plugin is more than a protocol version bypass. It actually translates newer packets to older clients (vice versa).
Please be aware that this plugin has to be updated with every new minecraft version. AnyVersion currently allows players to join with versions down to 1.20.60. Clients below 1.20.60 are no longer supported and are not expected to work.
If using WaterdogPE, you probably want to use SyodogPE. AnyVersion works with base WaterdogPE, but your WDPE console might get spammed with some warnings you can just ignore.