There is no hard requirement to use APCu. Also, if you don’t want to enable it globally you can just run every Nextcloud related command with the apc.enable_cli=1 option. In order to make things easy, you could create two bash aliases in ~/.bash_aliases, like this:
alias nocc="sudo -u www-data php --define apc.enable_cli=1 /var/www/html/nextcloud/occ"
alias ncupdate="sudo -u www-data php --define apc.enable_cli=1 /var/www/html/nextcloud/updater/updater.phar"
…then you only have to type ncupdate and nocc upgrade in order to upgrade your instance.