It's not a scam, if it is showing at the top of your eBay Overview landing page, usually in a red, thin banner.
That notification is shown to new members, and those returning after a few months break from selling, to update their registration for eBay's Managed Payments.
See here:
You need to provide eBay with details of a bank account and have this account verified. The usual method here, is for eBay to send 2 micro deposits into that nominated bank account for you to receive, and confirm to eBay.
This will show you how to register for eBay's Managed Payments.
https://www.ebay.co.uk/help/help/selling/getting-paid/introducing-managed-payments-ebay?id=4795
You can always contact Customer Services to be sure they sent the message, it's not easy to do so, no direct link but you have to persevere, keep asking the bot to speak to an agent, and they do eventually put you through.
Lines open at 9 a.m. on weekends.
https://www.ebay.co.uk/help/eua?id=5275&mkevt=1&mkpid
@breas_6739
You may also be notified to provide your NI number, also not a scam, it's information required to be passed on to HMRC.