Can't activate Multiplayer Game if the Super Mario Mash-up resource pack is activated

I have reproduced the bug trying to update the issue in hope so Super Mario Mash-up Pack can be used on cross-platform multiplayer (crossplay), and so I can confirm this bug is still ongoing.

Though the original author had put the workaround to this issue, since the original author did not put a clear way to reproduce the issue, here's mine:

Currently, the resource pack from Super Mario Mash-up Pack on Nintendo Switch disables all forms of multiplayer instead of setting multiplayer to Nintendo Switch-specific (or even allowing cross-platform) when toggling multiplayer on Super Mario Mash-up Pack world template, or simply having it's resource pack applied / activated when creating a custom world in Create New World screen. A pop-up about removing resource pack / disabling "cross-platform multiplayer" also appears when you try to switch on multiplayer when disabled or apply the resource pack from Super Mario Mash-up Pack.

There are 2 methods to reproduce, with one recently discovered by me and the original done by the reporter, and either one can be done,

Method 1: Using world template of Super Mario Mash-up Pack:

1. With Minecraft open, click "Play",

2. Click "Create New",

3. Click "Super Mario Mash-up Pack" as this currently is the only world with unlawful restriction applied,

4. If the popup appears, proceed by clicking "Continue",

5. Find and click "Multiplayer",

6. Turn off multiplayer toggle,

7. Try to turn multiplayer back on.

Expected result:
the toggle can be switched, the game won't ask you, or at worst, the game tells you that it will only host in Nintendo Switch specific multiplayer (online play).

Actual result:
the game asks you that it has to have the resource pack disabled while creating, despite it could be used on Nintendo Switch specific multiplayer while creating the world with it in older versions or workaround done below.

Method 2: Original from the author, creating own world and activating the resource pack from Super Mario Mash-up Pack:

1. With Minecraft open, click "Play",

2. Click "Create New",

3. Click "Create New World",

4. With Create New World screen loaded, Find and head to "Resource Packs",

5. Go to "Available" tab,

6. Press the dropdown of "Owned",

7. Add the resource pack "Super Mario Mash-up Pack" by pressing "Activate" on it.

Expected result:
the game won't ask you, or at worst, the game asks you that it had to disable cross-platform multiplayer (crossplay) when the resource pack was being applied. and when applied (activated), regardless it had unlawful restriction or not, multiplayer in Multiplayer tab can still be toggled (the only difference was if the world was hosted in cross-platform multiplayer or Nintendo Switch specific multiplayer by the game).

Actual result:
the game asks you that it has to disable cross-platform multiplayer, but if you clicked "Turn off multiplayer and apply pack", it disabled all forms of multiplayer, re-enabling it requires the resource pack to be removed (deactivated), despite it could be used on Nintendo Switch specific multiplayer (Online play) in older versions or with the use of workaround below.

Workaround to both methods: After the world was created, exit the world to return to Play screen (by clicking "Save and Quit"), then click the pencil icon (Edit) and enable multiplayer back on in Multiplayer tab, though currently only hosts in Nintendo Switch specific multiplayer. This workaround may not be performed as of 1.21.43 Hotfix for A/B testing.

Additional context: Based of a solution of my duplicating bug MCPE-181869, if the Super Mario Mash-up Pack was usable on cross-platform multiplayer (Crossplay) (forgot to mention, and even be usable on other platforms), then this bug would be effectively fixed.

Update: Off-topic but Skins from Super Mario Mash-up Pack are also affected, by just equipping one, and then try creating any world, Multiplayer toggle is completely locked disabled with no way of re-enabling without switching away the skin (based of my duplicating bug MCPE-181869), even for Nintendo Switch specific multiplayer, however creating the world does not actually have multiplayer disabled (and so having it re-enabled), otherwise the same workaround shown above can be performed.

Overall, Can confirm for me. And the issue can be reproduced in other ways, but needs clearer explanation on how to reproduce, which for bug tracker staffs / moderators, can look at the first comment of this issue from me for how.

Off-topic but if based off my duplicating bug, there is for now a workaround to the skins by relying on bug MCPE-181194.
To workaround this, you'll need to have a skin from Super Mario Mash-up Pack equipped on one of profiles in Dressing Room before having the game updated to latest version, then with the game's updated, join in or enter the world without equipping the skin, as otherwise it still will cause pop-up or have multiplayer forcefully disabled, after that, switch to the skin you want to use.
Video of me doing the workaround can be found here
Update: as MCPE-181194 was fixed via the backend change, this workaround is defeated.

Affects 1.21.43 Hotfix, and the workaround of re-enabling Switch-specific multiplayer with the resource pack from the Super Mario Mash-up Pack is defeated. However there's a PSA for the Mario Mash-up indicting that Mojang was aware of likely MCPE-185721 and was putting the update in some time (Nintendo Switch only):
"As you were playing the Super Mario Mash-up Pack, you might be aware that newly added items and mobs weren't updated (retextured) at immediate. But don't worry, the update's coming soon. Thanks for the patience of our work!" (Translated from the image below)

(Sorry for foreign language)

Update: Interestingly, I can then view it again on my PC, and there's one, "No matter you were just building a cobblestone castle as a player, or as a developer programming something, making things take time..." (translated from the image below); Developing is widely available on PC, so this bug could be fixed and that would be amazing if it meant the pack would be made available for PC and mobile.

(Also Sorry for foreign language)

Update: Affects 1.21.44, maybe the issue would be fixed in the next minor update at latest

Thank you for your report!
However, this issue is Working as Intended.

The report you have submitted is working as intended: As design.

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Oh no...
According to the bottom of Different Minecraft Versions from Minecraft Help:

• The Super Mario Mash-Up is playable only by Nintendo Switch owners in single-player, split-screen, local network, and over Nintendo Switch Online.

By the description from Minecraft Help above, worst case scenario, I expected only Nintendo Switch specific multiplayer to able to be enabled while playing with the Super Mario Mash-up Pack.

And in former versions and Edit World Screen (under JSON / old UI), Multiplayer game can be enabled, even though it does not allow cross-platform multiplayer to be enabled, it just enables Switch-specific multiplayer, this bug just straight-up disallows Switch-specific multiplayer. Which contradicts the one from Minecraft Help.

Update: Just worked around the bug by setting it to local play, but that only allows other Switches to join, however somewhat consistent to ones from Minecraft Help.