The Touch Bar was available exclusively on some MacBook Pros sold between 2016 and 2019. It has been 5 years since Apple released a new device that had one. Approximately half of the MacBook Pros that came with one no longer receive macOS updates due to Apple now considering them obsolete as a result of their age.
There is absolutely no chance that as many as 1% of Vivaldi users have a Touch Bar on their device, and the percentage of even Mac user that have one will be in a steep - and irreversible - decline.
Any development time invested on the Touch Bar would be disastrously inefficient.