Downgrade / Starting drive missing

Hi !
Installed Sequoia OCLP on MBP 2011 and not really keen on... May be it's too much to handle for that kind of computer.
Hence, I tried to downgrade booting a new USB disk with Sonoma, but it refused to install it.(Yes I transfered the boot the internal disk prior).
I so tried the internet recovery of Lion. So far it downloaded it but when I had to choose a startn drive where to install it... There was none... NO disk at all.
Would there be a genius among you ? :-)
Thanks !