Yup, the no tax rises for working people was a stupid thing to put in the manifesto. Labour would have won anyway given how Rishi lost a huge amount of Tory voters.
A small tax rise across everyone is probably acceptable, but as usual, if there are lots of exemptions for certain groups/demographics, it won't be popular. The broader the better, so maybe a percent or two on VAT rather than income tax.
Or if they're going to change income tax, then scrap NIC and raise income tax by a few percent so that "working" people aren't hammered, i.e. reduction in partly compensates the increase in income tax.