everything you said is more or less right, but not everything is a problem.
- There are more difficult to buy, as they are a b2b product, but on amazon they sell some models.
- brightness is higher, depending on the purpose of the monitor, there are monitors for sun facing storefronts, which are way brighter, but those also have fans and are noisier. The ones purposed for indoor are more or less the same brightness of the tvs, and sometimes have sensors for changing the brightness depending the environment, which is actually a plus.
- no antenna, some offer iptv, and others actually are android or linux based, so you may even install some apps, but you must configure them manually so much easier to use an external player.
- they are tougher panels, but they are designed for showing ads and static content, so no dark blacks, less contrast and usually less colour gamut coverage.
- not many 4k panels, the are designed to see from a distance, so many are fhd instead of 4k.
- another drawback is that many doesn't have speakers, so you have to hook up your own sound system.
Anyway, I'm in front of a storefront samsung om55n and watched some content and it's ludicrous, at night and the room seems illuminated like during the day.
Samsung also has a business line of tvs, are more like the domestic ones but designed for longer operating times and you can configure them to show slideshows or to have a ticker overlaped. They use the same basic tizen system, but the home screes is different and I doubt you will find ads on them.