The old macOS 10.15 machine I was using for testing Vivaldi has been upgraded, despite not supporting newer macOS versions.
It actually can run @Vivaldi 7.0 despite reports to the contrary you might have heard.
https://vivaldi.com/os-support-notice-10-15/
ℹ️ I went with the third option (🐧) under "What can you do now?" in the above article. 😉