I have contacted multiple companies. Some of them have ignored my emails when I had been making odd requests and asking odd questions. However, I have had immediate responses from all non-Chinese companies when asking for service on products that I already purchased, which seems to be a priority focus for most companies.
Companies that contacted me immediately for product support were Schiit, Audeze, Monoprice.
Companies that contacted me immediately for odd requests and odd questions ZMF, Audeze, Schiit, Burson, TTVJ.
You can get a very good feel of which companies are good from the forum members. There is also a thread where feedback is shared;
The truly bad customer support companies have well known reputations, such as Questyle. Sometimes I am very excited and eager and I try to have patience with companies. Especially with the demand and supply chain problems that have cropped up. I just take a step back and take a breath. There are lots of people here to help us.