Career Advice. Changing jobs right after starting

Hi everyone, just wanted to get a bit of career advice specially from more senior members.

A bit of background:

I am an engineer in my early 30s, who just made the move to finance after trying for a long time. I started in a very niche field as an intern, which rolled into a fixed term contract. After a year at that company it I lost my job due to Covid and general layoffs.

Few months after losing my job I found an internship in the same field, I applied to it thinking it would keep me busy waiting for that niche to pick up, but after six months and due to industry conditions, the project was cancelled and wasn't renewed. This was a year ago and since then, very few roles have come to the market at junior level. I was tired of waiting for this niche to pick up so I decided to diversify into other fields and finally got a job at a big European bank, which I accepted, and will start next month. It is a credit analysis role and I think I will enjoy it, but the pay is really low, I'm getting paid fresh grad money at a not-major European hub. I was decided to take it and build my CV up but I just got an offer for an internship in the field I already have experience in, and need to decide what to do.

It should be an easy pick, a permanent role vs an internship, but keep having second thoughts. On one hand I don't need another internship in my CV, plus nothing guaranteed at the end, but on the other hand it pays way more than the bank and my year of experience is directly applicable. Besides that, I am starting at the bank next week, and I would have to leave in a months’ time, and not sure how will they take it. I could see myself staying at the bank if they matched the compensation, but I can't stay for 2, 3 years at a place I know I am making 50% of what I could be making. I could stay maybe for a couple months, but what good would that make to my CV if I am changing jobs again after a few months and cannot show any progression.

I guess I am just looking for opinions from people more experienced than myself.

BTW I just got an email today for an interview again for my field at a bank in London and this time not an internship, but will have to start the process as I start my new job. Should I tell them I am just starting a new position or hide it? Would it make me look unprofessional leaving a job right after starting? Should I jsut keep the role I have even if the pay is too low?