I have a Gigabyte B550m H, and I don't know what other option there is, I went to Settings-AMD CBS-NBIO Common options-GFX Configuration, I changed it to UMA_SPECIFIED and I put 2gb on it.
The route with OI Ports is similar, Settings-OI Ports-Integrated Graphics, I choose Forces, then UMA Frame Buffer Size and I choose 2gb.
What I realized is that when I let the pc turn on and off to go back to the BIOS, the options that I change in NBIO Common options are reset, it goes from being in UMA_SPECIFIED to AUTO.