The population of browsers and things that don't understand TLS1.2 is miniscule now, so there should be no impact in disabling tls1.1 and below anywhere possible.
Browsers aren't to the point here, it is referring to servers seeking to verify control of a domain, by conducting a “acme-tls/1” handshake initiated by the Let's Encrypt issuance server.
If such a server only supports TLS 1.1, then TLS-APLN-01 validation will fail after this change is implemented.
Nobody should be running tls1.1 only (and incapable of opportunistically negotiating for 1.2 or 1.3 instead) on their public facing httpd in 2022, I disabled everything below 1.2 on some rather high traffic websites several years ago with zero impact.
If such a server only supports TLS 1.1, then TLS-APLN-01 validation will fail after this change is implemented.