Hello there, what is the best way to check the submitted trx status from web-app without infinite loops and seqno/trx hash comparisons?

if you need it for handling payments, use a ready-made solution - https://github.com/TheTonpay/tonpay-js-sdk

Ty, yes, it is for handling payments.

Do you know how to integrate that invoice abstraction and isPaid() status check with TONConnect ui?

I can help you with the integration in dm

kk