You have to look in the Izzy repo.
Unfortunately you probably won’t find any place to really buy it anonymously. If you have some crypto already you can buy some but without it, you will have to go through some broker.
In the US, know your customer is a big thing so you have to ID yourself before you can buy from the more legitimate companies.
Yes, but its not supported on everything. I use Yubikeys since they support more interaction types. I personally use them to lock my more important things when I can. Like my password vault, financial sites, emails, accounts, etc.
For the accounts that are whatever, less important I use OTP. You can also store a limited amount of OTP tokens on the Yubikey and use their open source software to view the codes.
ALWAYS buy a backup if you do end up locking accounts with it, just in case you lose it. It is more secure than having a code saved digitally as you need the physical key to unlock things.
Mostly their marketing practices. They are designed well but mostly designed to keep you locked in one way or another.
For me, their desktop is not as intuitive as people make it seem and lacks simple shortcuts that most other desktops have.
On mobile, its the restriction of customization and options. They are getting better at customizing but still limit you on options for anything outside of their apps. They claim to be private but follow similar practices as other companies, just in a more quite way with better PR.