1. Most carrier locked phones can be unlocked.

2. Locking the bootloader is a security feature specifically to prevent people who don't know what they're doing from downloading malicious apps. If you do know what you're doing it's reasonable to say that you will buy a phone where the bootloader can be unlocked, and are capable of unlocking it which is actually a relatively straight forward process.

3. Your posts are visible to Lemmy users who aren't members of your community, just FYI.

https://www.consumerreports.org/electronics-computers/cell-phones/how-to-unlock-your-phone-from-any-major-carrier-a2778672129/

Carrier locks that you can't get unlocked are almost always because they didn't actually pay for the phone. The "cheap phone" is subsidized by the high monthly service cost and having to be subscribed for x amount of time is part of the deal.

they are illegal in Australia.... I remember how crap it was when it wasn't...

In France (it might be a European thing, others will maybe confirm), carrier phones have to be ulockable after 6 months (assuming they're still locked to begin with) . Just ask your carrier and they'll unlock it.

Of course it's best to buy hardware outside of their ecosystem to begin with.