Under the government’s Smart Export Guarantee (SEG), energy suppliers like Bulb offer payments to small-scale green energy producers for putting electricity onto the grid. You can read more about SEG on Ofgem’s site.
SEG was introduced following the closure of the Feed in Tariff (FIT) scheme. If your generation installation was certified after 31 March 2019, you won't be eligible for FIT. But you can get payments for the energy you export to the grid through a SEG scheme like Bulb’s Export Payments.