I have seen a lot of threads talking about mud, making mud pits, heating mud, finding mud, mixing mud, etc. I collected a bunch of links. Disclaimer - I don't have any experience with mud. Also, I use "mud" when I mean any type such as mud made from pottery clay, bentonite, kaolin, natural mud, or anything.

Acquiring Mud:

https://umd.net/forums/buying-clay-in-bulk
https://umd.net/forums/making-mud-from-potters-clay
https://umd.net/forums/best-clay-for-an-indoor-mud-pit
https://umd.net/forums/potting-clay-help
https://umd.net/forums/what-mud-to-use-in-a-peat-pit
https://umd.net/forums/clay-mud-recipe
https://umd.net/groups/i/mudclay-supplies

Making a mud pit:

https://umd.net/forums/how-to-make-a-mud-pit
https://umd.net/forums/how-to-make-a-mud-pit-2
https://umd.net/forums/how-to-make-a-clay-pool

Mixing Mud:

https://umd.net/blogs/how-to-make-mud-from-dry-clay

Coloring Mud:

https://umd.net/forums/changing-colours-of-clay

Heated Mud pits:

https://umd.net/forums/a-guide-to-heated-mud
https://umd.net/forums/my-diy-custom-heated-mud-pit-build

IBC Tote Mud Pit:

https://umd.net/forums/diy-mud-pit

Stella has also made IBC Tote Mud Pit if anyone wants to see an example:

https://umd.net/profile/i/stella/section/scenes/scene/backyard-mud-pit-9--building-a-peat-pit/backyard-mud-pit-9--building-a-peat-pit
https://umd.net/profile/i/stella/section/scenes/scene/backyard-mud-pit-10--stella-tries-it-out/backyard-mud-pit-10--stella-tries-it-out
https://umd.net/profile/i/stella/section/scenes/scene/backyard-mud-pit-11--barley-gets-fucked/backyard-mud-pit-11--barley-gets-fucked

Pumping Mud:

https://umd.net/forums/mud-pumps-and-shower-design

Instant Mud:

I don't know if there has been any posts about it, but you can buy instant mud from messysupplies:

https://www.messysupplies.com/products/mud

Here are some examples of instant mud:

https://umd.net/profile/i/stella/section/scenes/scene/stella-tries-instant-mud/stella-tries-instant-mud
https://umd.net/profile/i/amylith44/section/scenes/scene/mud-monster/mud-monster

Finding Mud:

https://umd.net/forums/finding-mud-quarrypitsflats
https://umd.net/forums/where-do-i-look-to-find-good-mud
https://umd.net/forums/five-ways-to-find-mudquicksand-in-your-a
https://umd.net/forums/finding-mud
https://umd.net/forums/finding-mud-2

Advice for mudding:

https://umd.net/forums/outdoor-mud-clean-up
https://umd.net/forums/mudding-tips
https://umd.net/forums/mudding-advice-and-tips-needed
https://umd.net/forums/mud-larking-logistics

Other:

https://umd.net/forums/i-need-help-people-that-know-about-clay
https://umd.net/forums/i-need-some-help-making-an-indoor-mud-de
https://umd.net/forums/looking-for-quarry-mud-in-central-canada
https://umd.net/forums/question-for-mud-fans
https://umd.net/forums/storing-mud-and-heating-it
https://umd.net/forums/clay-materials-and-safety

These ones are posts that I could find in search or remembered. Feel free to add links.