Do self-employed people have to provide their own reasonable adjustments?

I am self-employed, had a 2 hour long in-person assessment, sent in a full DSE workplace assessment report and letters from my psychiatrist and GP that connect the items I applied for to my conditions and yet my case manager refused all the items apart from 1 (ergonomic chair).

The excuse is that they should be reasonable adjustments, apparently. But I have no employer to provide these and believe that self employed people are still supposed to be able to get support with non-standard items that connect to their disabilities.

I will be sending them an email asking them to reconsider. My case manager never even spoke to me about how my conditions affect me.

Are self-employed people supposed to provide their own reasonable adjustments? I was under the impression that even in employment settings reasonable adjustments were things like wheelchair ramps and flexible schedules.

I work for other people on a self employed basis and do not pay my own salary nor use PAYE. I do not own a company and I am not my own employer. Instead, I have a UTR and work on a freelance basis.

I applied for specialist equipment to help me work without pain due to my joint conditions and Hypermobility syndrome, as well as cognitive needs and sensory issues caused by autism and ADHD.