Mattress advice wanted (again) - soft beds for sore MEeps

[river]

Here we go again.. This question is the opposite of the one I posted previously lol.

My partner has chronic post exertional muscle pain and fatigue.
They are wondering if a very soft mattress (either mattress by itself or mattress + topper/2 mattresses stacked) would help.
They currently have a memory foam mattress from ikea but don't like it much because it needs flipping regularly.

Has anyone found a soft mattress (or any other configuration) helps with muscle pain? Any ikea mattresses you like?

[emsarah]

@river a family member of mine has fibromyalgia so lots of constant muscle pain. They got the top level Noa mattress (most padding) and added a thick wool mattress topper (fluffy kind).
From their experience I would recommend the online mattress route because you can actually try the mattresses for 3 months and return them if they are not suitable (this family member did it with the Eva mattress which was too firm and uncomfortable). Brands to also look at I think might be Sleeping Duck or Koala who just released new types.