CAN'T ADD A CNAME AT THE ROOT IN A BUDGET REGISTRAR. NOW WHAT??

simple goal: example.com and www.example.com should both show my site on a git-based pages host... reality: the apex throws a certificate warning.

This site can't be reached
Check if there is a typo in my-shop-site.example.
If spelling is correct, try running Windows Network Diagnostics.
DNS_PROBE_FINISHED_NXDOMAIN

i tried adding the CNAME at the root anyway, a budget registrar threw an error.. 🤷 i tried a URL forward but that seems to break HTTPS... i keep reading about ALIAS records and CNAME flattening and i'm lost. Which option is teh clean one? Clear recommendations welcome, i'm tired of half-working setups. pls help 🙏