Funny thing… When I looked at the source where arm64/aarch64 versions for L5 TorBrowser were made available, I found that the maintainer has added Mullvad there too. Take a look and report back: Tor Browser Ports - Browse Files at SourceForge.net
Edit to add: Mullvad seems to be doing well in the recent privacy comparison list at https://privacytests.org/ as far as “(by) default” desktop browser go. In “privacy modes” list Brave on Tor seems to compete well.