Google has to unlock 5G for the carrier. Since the Pixel is not officially available in Switzerland, Google has not (yet) done this.

Unfortunately, I can only speak for Sunrise, not Swisscom. But: 5g didn't work with my 2-year-old SIM card. The shop wanted to change the card, so I thought, why not go straight to eSIM. Unfortunately, still no access to the oh so praised 5g network of Sunrise. I'm really hoping for an update from Google.

As of today, my Pixel 4a 5g also has Swisscom 5g reception. I'm happy.

Since the last update, my Google Pixel 5 actually displays 5G with Swisscom. After a few tests, however, I realise that no faster data rates vs. LTE are achieved with it, but remain practically identical. This statement applies to the Zofingen location for the time being.

Google no thanks 5G doesn't work.

Addendum: You probably won't find much support from any provider, as it's not a mainstream device like the Samsung S20.