This product requires a KID in English or in a language approved for your country.
Answer. You need to have Interactive Brokers PRO account.

So you are European and try to buy any Index fund on Interactive brokers and then you get this message:
Trading Restricted
This product requires a KID in English or in a language approved for your country. Retail clients can trade packaged retail products only if an appropriate KID is available. More information is available in IBKR Guide.
Answer: You need to have Interactive Brokers PRO account.
How to get Interactive Brokers PRO account
The professional status to get the privilege to trade US ETFs without KID. In IBRK->Settings->MiFID Category you can change your User Category from Retail to Professional. You need to fulfil two out of three conditions (it is also well explained on the MiFID-Category site):
- Account balance over 500.000€. Regardless if it is in Interactive Brokers or at another bank.
- You work or have worked in the financial sector for at least one year in a professional position
- Carried out transactions, in significant size (i.e. value of trades totalling EUR200,000 or more) on the relevant market at an average frequency of 10 per quarter over the previous 4 quarters
If you fulfill two points you will be categorized as a professional and you are able to trade the ETFs you have mentioned above.

IBKR Support
TLDR: Contact the firm in question and ask them to publish an English KID document on their website. If they do that, the ban will be lifted by IBKR. I already contacted Pimco but the more people write, the bigger the chance that something will actually happen.
full response by ibkr:
Thank you for contacting Interactive Brokers Client Services. Interactive Brokers is required to provide European Economic Area (EEA – the 27 member states of the European Union, as well as Norway, Iceland and Liechtenstein) and United Kingdom retail customers with Key Information Documents (KID) for certain financial instruments. Relevant products include ETFs, Futures, Options, Warrants, Structured Products, CFDs and other OTC products. Funds include both UCITS and non-UCITS funds available to retail investors. Since clients of Interactive Brokers have agreed to receive communications from Interactive Brokers in English, currently our clients resided in the EEA or in the UK can trade the products detailed above if the relevant KID is available in English or in any official language of the country of their legal residence. For more information on KIDs please read our Knowledge Base article: LINK../4718 Opening orders from Retail investors residing in the European Economic Area (EEA) or the United Kingdom that are associated with a product that does not comply with the EU's Packaged Retail and Insurance-based Investment Product Regulation (PRIIPS) will be rejected. The regulation is intended to enhance understanding of these products through provision of disclosure documentation referred to as the Key Information Documents (KIDs). The KID provides information such as product description, costs, risks and performance. Most US-issued ETFs do not currently have a KID, but a large number of EU or UK-issued ones do. You can find more information on the details of the PRIIPs Regulation by clicking the following link: LINK../2993 These rules apply to all retail clients residing in the EEA or the UK and also to corporate accounts classified as MiFID Retail. Customers residing in the EEA or in the UK who are classified as a MiFID Professional are not affected. If you think that an English language KID is available for, PDO (ISIN: US69355M1071), please send us the links to the document in your reply and I will ask our responsible department to remove the restrictions for you on the product if possible. Typically, you can access KIDs on the issuers’ websites. We look forward to hearing from you soon.
More information in Reddit post