how do you legally accept money then?

clarification: i'm in EU

In the US, anyone can sell good or services and do business without formally registering as a business. You're automatically classified as a sole proprietorship, with your legal name as the business name. But there's no liability protection, since you and the business are the same legal entity. That's where LLC or incorporating comes in, along with lots of other reasons to want to formalize the business as a legal entity.

If your turnover is low enough you don’t need to be VAT registered in the UK. Also, in the UK you can be VAT registered and be a sole trader.

do you think as a foreign citizen i'd be able to setup a UK Limited?

i'm familiar with Companies House though

If you’re not on any sanctions lists there shouldn’t be any issues.

Your residency/citizenship does not play any part in forming a UK LTD. It might affect your ability to open an account with some banks though.

These guys are okay https://www.99pcompanyformations.co.uk/ The whole process takes a few minutes and costs almost nothing.

Are you in the EU or the UK?

I think you just take the cash using Stripe or whatever. It gets deposited in your bank account and you claim income tax on it.

i don't want liability

What are you talking about? You make revenue, you disclose the revenue, you file taxes. Doesn't matter if you do it as a private person or as an LLC.

You can incorporate to reduce liability easily, it does not cost a lot of money in most jurisdictions.

You have personal liability either way if you are the one writing the code, marketing to customers, etc.