Despite it saying its 1.16.2 the versions 1.1.5+ have their version dependency removed meaning they should load in other versions fine. Keep in mind though that its only tested in 1.16.2 and using it elsewhere like in e.g. snapshots might break.
If you wanted to make a public server thats not Bukkit/Spigot etc. you will quickly run up to the problem of not having proper protection of your world since other type of modded servers have as good as no protection mods. With Flan worry no more.
Flan (Fabric LANd) allows you to create and manage claims on your minecraft world. With commands, gui and world interactions you can easily create and manage those. Flan is completly server side only meaning you could setup a fabric server with Flan and connect with a vanilla client and it will work just as fine.
Claims are pieces of land with restricted permissions to prevent griefing with a default depth of 10 (configurable) which means they extend 10 blocks downwards from the claiming spot but no limit upwards. This makes it so it wont affect mining below claims but claims will extend if players start building below. They support subclaims to create town like systems where subclaims have their own permissions too. Being in SubClaim-Mode allows you to edit subclaims (how to down in commands). If you are an admin you can create adminclaims too where only admins (with permission level 2+) can modify and have full access to those.
To create claims you right click with the claiming tool (a golden hoe by default) on a desired block to set the first corner and right click on another position to make the claim. You might know this from other bukkit plugins:
Standing in a claim you have permissions for allows you to open up the claim menu via "/flan menu"
With the menu you can edit global permissions or specific group permissions. Groups are well... groups you assign players to to allow them have custom permissions on your claim. Group permissions have the states: default, true or false where default goes back to the global permissions
Various permissions are included such as pistons cant push/pull across claim borders, water not crossing claim borders, tnt explosions and many more.
List of commands Flan offers in form of /flan <command name>:
menu: when standing in a claim you have permissions for opens the claim menu
claimInfo: prints infos about the claim you're standing in
delete: deletes the current claim
deleteAll: deletes all your claims (you need to double type to confirm it so no accidents)
deleteSubClaim: deletes the current subclaim
deleteAllSubClaims: deletes all subclaim of the current claim
list: lists all claims you have. if op also gives ability to list other players claims
switchMode: switch between normal and subclaim mode
group add|remove <name> : adds/removes the group with that name. Also editable via the claim menu.
group players add|remove <player> [overwrite]: adds/remove a player to the group. if overwrite then will overwrite the players current group else does nothing. Also editable via the claim menu.
transferClaim <player>: gives ownership of the claim to the specified player. only works if you're the claim owner
addClaim <x y z> <x y z>: creates a claim with the given positions. same as using the claim tool
editPermission global | (group <name>) <permission> true | false | default: sets global/group permissions. Also editable via the claim menu (for group perm right click on the group in the menu)
Admincommands (in form /flan <command> too):
reload: reloads the config ingame
adminMode: switches to admin mode ignoring all claims
readGriefPreventionData: parses data from the GriefPrevention plugin to Flan
setAdminClaim: sets a claim to an admin claim
listAdminClaim: lists all admin claims in the current world
adminDelete [all <player>]: force deletes the current claim or deletes all claims from the specified player
giveClaimBlocks <amount>: gives a player additional claim blocks