I have noticed recently that it is no longer possible to pay for items bought through AliExpress by PayPal unless you sign up to payments by instalments. No interest (at face value).
No idea why but it worked well for me when I bought my mount. so long as it's under $2000
I also purchased an item with paypal the delivery guy was so incompetent I requested a refund from paypal which they did, then I could have made a profit as Aliexpress also offered a refund for non delivery. (I'm too honest)
Edit: I just checked, it depends on the seller if they determine 4 payments or a single payment, I just tested with this:
I have used paypal for AliExpress numerous times in the past but haven't purchased anything recently.
I did want to purchase a 25-50mm micrometer but haven't gotten around to it (I had one somewhere, once upon a time).
Use the Ali Express Web page and not the APP. The APP seems to have a bug. If you go thru their web page the normal PayPal option is available.
I had 2 Pay in 4 orders before I found this out. I am now using Chrome for Ali Express. I stopped using the APP for this reason.
Paypal can still be used, If you go to the payment methods box during the purchase, there is a barely perceptible "scroll down" arrow. I think thay have tried to hide it to avoid fees structure, but it's definitely there.