Pickysaurus

Unfortunately, it would seem your connection is the issue. If the download is corrupt at the end of the process it means there has been significant packet loss. 

The FOMOD is invalid (as the error says). Here's a more in-depth explanation. https://modding.wiki/en/vortex/developer/mod-installer-repair

If you're clicking "Check for updates (Full)" that would be why it's so slow. This does manually check each page, the optimised version should be considerably faster and just as accurate. 

Vortex downloads extensions it requires to function automatically. You should just leave them alone. 

This looks like a case of broken .NET 6 or C++ Redistributables - or just borked permissions on your install location for Vortex. Did you install Vortex to Program Files (as is recommended)? 

Borderlands 2 is not supported by Vortex.
You can see a list of supported games in the "Games" tab or by looking here: https://www.nexusmods.com/about/vortex/

Try logging out and back into Vortex. It looks like your session may be corrupted. 

Right-click on the collection in the Mods table. An option to do this has been added in one of the latest releases. 

Settings -> Interface -> Enable Profile Management

I'm not sure what users are doing to cause this. Make sure you have the latest version of Vortex. Every report I've seen so far was an outdated copy of Vortex and was fixed when they updated 

Skyrim SE and VR use the same section of the website and always have, so the downloads appear for both games. 

If you click the "Group" button on the category header you can achieve pretty much exactly what you're asking. 

 
If you don't like the site-given category you can also create your own. 

This is a bug introduced by a website update this morning. We're fixing it now. Sorry about that! 

This issue was resolved years ago. If you are still seeing it update Vortex to the latest version and ensure that you uninstall any old BG3 support extensions from the extensions section. 1.5.3 is the latest version. 

NMM hasn't been supported since 2016. If you need help with it you'll need to contact the current maintainers. 
Vortex has an option in the downloads section of Settings to control if it handles downloads from the site or not. 

After looking at the results of the test I did yesterday, we've decided the best course of action right now is to increase the daily API quota from 10,000 to 20,000. This should allow 2-3 large collections to be downloaded per day. 
While it is still possible to hit the limit, it should be harder to do so. 

This is a detection issue, it looks like your EXE file is different. 
You can report it to the extension creator here: https://www.nexusmods.com/site/mods/1058

Please see this thread for info on this issue: 
 

The automation settings do not apply to collections, they never have. 
Those errors are usually suppressed though, restarting the app might help. Some of them will show regardless though - the downloads not finalised ones are important so they appear when you download a corrupted file. 

You can install game extensions directly from their associated download page if your setup is so messed up you can't find it in the app. 

https://www.nexusmods.com/site/mods/196

We won't be building this into Vortex, but it may be possible to add it to our new app when that is fully developed. 

You should never remove these files manually, it should be done in the Vortex UI.
If you want to do this in batch Ctrl + A, Ctrl + Click and Shift + Click all work in the mods table. 

Please manually install the latest version of Vortex over your current install to fix this. 
You have a super old version that cannot auto-update. 

You have a very, very old version of Vortex installed. Please update to the latest version and try again. 

Go to the Games tab, find Subnautica, click the little menu on the card and select "Manually Set Location". Pick the folder for your Steam install and restart Vortex once it has been accepted.