I have never purchased Monero anonymously, I just buy it straight from fiat on Kraken.
What I do:
Fiat-->Kraken-->Monero-->Self-custody Monero Wallet
If you don't want anyone to know you purchased Monero(which is not necessary for most people because once you have the Monero, it's untraceable and all anyone can know is that you bought Monero, similar to how anyone can know you have cash once you withdraw from the ATM, but it's untraceable) then the easiest way would be to buy a different crypto (that you are okay with bank/govt knowing you bought) and then swapping it to Monero.
Now, I don't know the extent to which you would be passively traced if you bought a traceable crypto like Bitcoin on Kraken, withdrew to CakeWallet and swapped on Trocador. It would depend on if the instant exchange on Trocador shares info with Kraken or they both use the same Chainalysis company.
What you could do to break the link is buy ZCash on a CEX like Kraken, withdraw to CakeWallet, shield it(I think it's automatically shielded, but Ive never used ZCash), and then swap on Trocador for Monero.
The idea here is that ZCash is more friendly to govt so they still know you bought ZCash, but after you bought it, it vanishes from their analysis.
Haveno/Retoswap is great, but I would not encourage it for your first time obtaining Monero because it is not easy for beginners and can be complicated. Also there was an exploit recently. I do think long-term it will be awesome.
> despite my misgivings about the privacy guarantees of RingCT
Yeah well fortunately we are upgrading to FCMP++[1]. Also, a lot of Chainalysis's tracing from this leaked video[2], highly recommend you watch, was based on malicious nodes. They implemented an IP blacklist for malicious nodes, but you can also use Tor for more protection. The best thing for would be to run your own node.
I have a node I host and if you contact me I can give you the URL–it's really fast.
I've given info about buying Monero in the past[3], but not your specific situation. You might find it informative.
[1] https://www.youtube.com/watch?v=jc8Kc0WogAI