>The article mentions sharding but sharding usually reduces security

I think if you're careful about it, sharding can be done without impacting security much. Suppose you would split the Bitcoin network exactly in half. Each half has only has as much hashpower, so you can attack it for half the cost. But each side also contains only half as much money, so the potential payout went down by the same factor as the price of attack.

Of course it's more complicated than that, because a realistic attack isn't about stealing money from everyone but from a handfull of large targets. Also, TON is proof of stake and not proof of work. And you have to scale sharding not with money present, but with transaction rate. And the shards (presumable sidechains?) will transfer money between each other, and you have to scale that as well. It's a complicated problem, but I wouldn't rule sharding out as a viable approach.

I highly doubt they can do the promised "millions of transactions per second" in any realistic scenario, that would be a major breakthrough. VISA can only do 57 thousand transactions per second [1]. But I also don't think they need remotely that much. Paypal has an average transaction rate of ~200 transactions/second, VISA of ~1700 transactions/second. At least paypal's average rate would be achivable even with Bitcoin's codebase if you were to take some liberties with block time and size (which isn't entirely unreasonable, the internet got faster in the last 8 years)

1: https://mybroadband.co.za/news/security/190348-visanet-handl...