If you are using JAVA+BEDROCK Combo (GeyserMC), you can still use the existing Minecraft whitelist system to prevent unwanted players to your server. However, as Java edition and Bedrock edition have separate player name database, they can often conflict with same player names. As such, every bedrock player will have a dot starting with the name. Eg .steve instead of steve
Example Commands to type in CONSOLE section of the control panel:
To add player to whitelist for JAVA players:
whitelist add playername
To add player to whitelist for BEDROCK (GeyserMC) players:
whitelist add .playername (Note the dot in front of the name)
Example: If the player is joining from a Bedrock edition, and his player name is: steve
Command would be:
whitelist add .steve
Don't forget to turn on Whitelist for your server for the server to start restricting all players but the ones listed in the whitelist