What type of salt for sourdough bread baking?

This may come across as a little cynical ;)

Don't believe the hype.
Salt is salt.

The difference between Himalayan, iodised & kosher is so small you'll never taste it. They're all 98%+ sodium chloride. To a 1Kg loaf you're going to add something like 10g salt.

As it will completely dissolve before you bake it, not even the granule size is important.

Any salt will do. The trick is figuring how much salt. If a formula is based on a specific salt, and you switch, you need to adjust. For example this author did a comparison. She weighed 1 level Tablespoon of various salts and found:

Iodized table salt 14g.
Fine grind Himalayan pink salt 12g.
French Fleur de Sel 11g.
Sardinian Black fior di sale 9 g.
Maldon Sea Salt Flakes 7g.
Diamond Crystal Kosher Salt 6g.

You need to adjust for this difference if using volumetric measures. Best to use a scale.

My understanding is that within some communities, it is believed that iodized salts slows down or kills the microbes.

This is not true, which has been shown a couple of times: studying sauerkraut and studying fermented cucumbers.

Himalayan salt is not really from the Himalayas, but from the Salt Range, which is nearby -not exactly 'Himalayan snow melt' (in fact an underground salt deposit from a sea that dried up hundreds of millions of years ago).

It has a bunch of impurities (or 'minerals'), which make it pink. It had no commercial value until recently when it became popular for Instagram. That's the value. It looks good in photos.

Salt is iodized for public health reasons. https://en.wikipedia.org/wiki/Iodised_salt#In_public_health_initiatives

Kosher salt is coarse and lacks iodine. It's for koshering meat, but the coarseness is good for some purposes (rubbing on meat). In the UK you can't buy it very easily, but you can buy coarse salt that's functionally identical (in that it's coarse and salt).

All work the same way. A fine salt and a coarse salt is handy to have. And a scale with at least 0.1g resolution to accurately measure them. Any time you are dissolving the salt, they are all identical, just make sure to weigh them - measuring cups and measuring spoons are bad.