Have tried different Backpack mods and they've worked fine.
The issue arises once you place a Jar on top of a Hopper. For some reason the game just crashes at that point.
Here's the log for reference:

crash-2020-11-05_04.03.54-server.txt

---- Minecraft Crash Report ----
// Hey, that tickles! Hehehe!

Time: 11/5/20 4:03 AM
Description: Ticking block entity

java.lang.ExceptionInInitializerError
at alexiil.mc.lib.attributes.item.mixin.HopperHooks.tryExtract(HopperHooks.java:87)
at net.minecraft.class_2614.handler$zzp000$onExtract(class_2614.java:538)
at net.minecraft.class_2614.method_11241(class_2614.java)
at net.minecraft.class_2614.method_11249(class_2614.java:109)
at net.minecraft.class_2614$$Lambda$5452/1514982901.get(Unknown Source)
at net.minecraft.class_2614.method_11243(class_2614.java:125)
at net.minecraft.class_2614.method_16896(class_2614.java:109)
at net.minecraft.class_1937.method_18471(class_1937.java:510)
at net.minecraft.class_3218.method_18765(class_3218.java:424)
at net.minecraft.server.MinecraftServer.method_3813(MinecraftServer.java:868)
at net.minecraft.server.MinecraftServer.method_3748(MinecraftServer.java:808)
at net.minecraft.class_1132.method_3748(class_1132.java:92)
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:667)
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:254)
at net.minecraft.server.MinecraftServer$$Lambda$4486/411990170.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)
Caused by: java.lang.IllegalArgumentException: The given interface net.minecraft.class_3954 is a superclass/superinterface of the base class class net.minecraft.class_2248 - which won't work very well, because it will override everything else.
at alexiil.mc.lib.attributes.AdderList.putClassBased(AdderList.java:220)
at alexiil.mc.lib.attributes.Attribute.putBlockClassAdder(Attribute.java:239)
at alexiil.mc.lib.attributes.item.ItemAttributes.create(ItemAttributes.java:146)
at alexiil.mc.lib.attributes.item.ItemAttributes.(ItemAttributes.java:89)
... 16 more

A detailed walkthrough of the error, its code path and all known details is as follows:

-- Head --
Thread: Server thread
Stacktrace:
at alexiil.mc.lib.attributes.item.mixin.HopperHooks.tryExtract(HopperHooks.java:87)
at net.minecraft.class_2614.handler$zzp000$onExtract(class_2614.java:538)
at net.minecraft.class_2614.method_11241(class_2614.java)
at net.minecraft.class_2614.method_11249(class_2614.java:109)
at net.minecraft.class_2614$$Lambda$5452/1514982901.get(Unknown Source)
at net.minecraft.class_2614.method_11243(class_2614.java:125)
at net.minecraft.class_2614.method_16896(class_2614.java:109)

-- Block entity being ticked --
Details:
Name: minecraft:hopper // net.minecraft.class_2614
Block: Block{minecraft:hopper}[enabled=true,facing=down]
Block location: World: (-235,64,198), Chunk: (at 5,4,6 in -15,12; contains blocks -240,0,192 to -225,255,207), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Block: Block{minecraft:hopper}[enabled=true,facing=down]
Block location: World: (-235,64,198), Chunk: (at 5,4,6 in -15,12; contains blocks -240,0,192 to -225,255,207), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Stacktrace:
at net.minecraft.class_1937.method_18471(class_1937.java:510)
at net.minecraft.class_3218.method_18765(class_3218.java:424)

-- Affected level --
Details:
All players: 1 total; [class_3222['Avemado'/242, l='ServerLevel[New World]', x=-232.50, y=64.00, z=200.50]]
Chunk stats: ServerChunkCache: 2209
Level dimension: minecraft:overworld
Level spawn location: World: (-240,63,192), Chunk: (at 0,3,0 in -15,12; contains blocks -240,0,192 to -225,255,207), Region: (-1,0; contains chunks -32,0 to -1,31, blocks -512,0,0 to -1,255,511)
Level time: 334 game time, 334 day time
Level name: New World
Level game mode: Game mode: survival (ID 0). Hardcore: false. Cheats: true
Level weather: Rain time: 171265 (now: false), thunder time: 93508 (now: false)
Known server brands: fabric
Level was modded: true
Level storage version: 0x04ABD - Anvil
Stacktrace:
at net.minecraft.server.MinecraftServer.method_3813(MinecraftServer.java:868)
at net.minecraft.server.MinecraftServer.method_3748(MinecraftServer.java:808)
at net.minecraft.class_1132.method_3748(class_1132.java:92)
at net.minecraft.server.MinecraftServer.method_29741(MinecraftServer.java:667)
at net.minecraft.server.MinecraftServer.method_29739(MinecraftServer.java:254)
at net.minecraft.server.MinecraftServer$$Lambda$4486/411990170.run(Unknown Source)
at java.lang.Thread.run(Thread.java:745)

-- System Details --
Details:
Minecraft Version: 1.16.3
Minecraft Version ID: 1.16.3
Operating System: Windows 10 (amd64) version 10.0
Java Version: 1.8.0_51, Oracle Corporation
Java VM Version: Java HotSpot(TM) 64-Bit Server VM (mixed mode), Oracle Corporation
Memory: 1551563232 bytes (1479 MB) / 2136473600 bytes (2037 MB) up to 4772593664 bytes (4551 MB)
CPUs: 16
JVM Flags: 5 total; -XX:HeapDumpPath=MojangTricksIntelDriversForPerformance_javaw.exe_minecraft.exe.heapdump -Xss1M -Xmx5120m -Xms256m -XX:PermSize=256m
Fabric Mods:
autoconfig1u: Auto Config v1 Updated 3.2.2
cardinal-components-base: Cardinal Components API (base) 2.5.4
cardinal-components-item: Cardinal Components API (items) 2.5.4
cloth-basic-math: Cloth Basic Math 0.5.1
cloth-config2: Cloth Config v4 4.8.1
fabric: Fabric API 0.25.0+build.415-1.16
fabric-api-base: Fabric API Base 0.2.0+9f0fb4b895
fabric-biome-api-v1: Fabric Biome API (v1) 3.0.0+8367596d95
fabric-blockrenderlayer-v1: Fabric BlockRenderLayer Registration (v1) 1.1.4+c6a8ea8995
fabric-command-api-v1: Fabric Command API (v1) 1.0.9+a4467d2a95
fabric-commands-v0: Fabric Commands (v0) 0.2.0+52d3083695
fabric-containers-v0: Fabric Containers (v0) 0.1.8+045df74f95
fabric-content-registries-v0: Fabric Content Registries (v0) 0.1.9+059ea86695
fabric-crash-report-info-v1: Fabric Crash Report Info (v1) 0.1.2+b7f9825d95
fabric-events-interaction-v0: Fabric Events Interaction (v0) 0.4.1+f8ac1db295
fabric-events-lifecycle-v0: Fabric Events Lifecycle (v0) 0.2.0+16acbe5b95
fabric-game-rule-api-v1: Fabric Game Rule API (v1) 1.0.3+a4467d2a95
fabric-item-api-v1: Fabric Item API (v1) 1.2.0+f8ac1db295
fabric-item-groups-v0: Fabric Item Groups (v0) 0.2.1+a4467d2a95
fabric-key-binding-api-v1: Fabric Key Binding API (v1) 1.0.1+730711c695
fabric-keybindings-v0: Fabric Key Bindings (v0) 0.2.0+3fa9f7c595
fabric-lifecycle-events-v1: Fabric Lifecycle Events (v1) 1.2.0+74cc3b2095
fabric-loot-tables-v1: Fabric Loot Tables (v1) 1.0.1+432ea18895
fabric-mining-levels-v0: Fabric Mining Levels (v0) 0.1.2+b764ce9995
fabric-models-v0: Fabric Models (v0) 0.1.1+f8ac1db295
fabric-networking-blockentity-v0: Fabric Networking Block Entity (v0) 0.2.5+b50ffc7b95
fabric-networking-v0: Fabric Networking (v0) 0.1.10+e00ecb5f95
fabric-object-builder-api-v1: Fabric Object Builder API (v1) 1.9.2+a89534ab95
fabric-object-builders-v0: Fabric Object Builders (v0) 0.7.1+a4467d2a95
fabric-particles-v1: fabric-particles-v1 0.2.2+fb0d9b0e95
fabric-registry-sync-v0: Fabric Registry Sync (v0) 0.6.1+a4467d2a95
fabric-renderer-api-v1: Fabric Renderer API (v1) 0.3.3+a4467d2a95
fabric-renderer-indigo: Fabric Renderer - Indigo 0.4.3+a4467d2a95
fabric-renderer-registries-v1: Fabric Renderer Registries (v1) 2.2.0+f8ac1db295
fabric-rendering-data-attachment-v1: Fabric Rendering Data Attachment (v1) 0.1.4+f8ac1db295
fabric-rendering-fluids-v1: Fabric Rendering Fluids (v1) 0.1.12+f8ac1db295
fabric-rendering-v0: Fabric Rendering (v0) 1.1.1+f8ac1db295
fabric-rendering-v1: Fabric Rendering (v1) 1.3.1+f8ac1db295
fabric-resource-loader-v0: Fabric Resource Loader (v0) 0.3.1+facf3bbf95
fabric-screen-handler-api-v1: Fabric Screen Handler API (v1) 1.1.0+8724984195
fabric-structure-api-v1: Fabric Structure API (v1) 1.1.0+f8ac1db295
fabric-tag-extensions-v0: Fabric Tag Extensions (v0) 1.0.3+ac8e8c5995
fabric-textures-v0: Fabric Textures (v0) 1.0.5+a4467d2a95
fabric-tool-attribute-api-v1: Fabric Tool Attribute API (v1) 1.2.4+2b46237995
fabricloader: Fabric Loader 0.10.6+build.214
inmis: Inmis 1.3.1-1.16.2
jankson: Jankson 3.0.1+j1.2.0
jumploader: Jumploader 2.0.1
libblockattributes: LibBlockAttributes 0.8.0-pre.18
libblockattributes_core: LibBlockAttributes (Core) 0.8.0-pre.18
libblockattributes_fluids: LibBlockAttributes (Fluids) 0.8.0-pre.18
libblockattributes_items: LibBlockAttributes (Items) 0.8.0-pre.18
libgui: LibGui 3.0.0-beta.1+1.16.2-rc2
minecraft: Minecraft 1.16.3
plantinajar: Plant In A Jar 1.8.0
universalcomponents: Universal Components 0.7.3+1.16.2
Player Count: 1 / 8; [class_3222['Avemado'/242, l='ServerLevel[New World]', x=-232.50, y=64.00, z=200.50]]
Data Packs: vanilla (incompatible), fabric/plantinajar, fabric/fabric-tool-attribute-api-v1, fabric/inmis
Type: Integrated Server (map_client.txt)
Is Modded: Definitely; Client brand changed to 'fabric'

Looks like I need to update LBA

Let me know if the issue still happens in the new update

Frickin' awesome! You're a true legend! Thanks a lot!
Awesome ass mod by the way!

Btw, is there a way to grow lilypads? You can certainly put them in the jar, unlike some other items, but with a water bucket as a base, nothing happens.