i think there must be some way (hopefully, depending on your contract with your provider) to have /gain access to your webspace. that would be the right place to enter those commands (take note that you should do that from the installing directory of your instance). it’s called bash or shell. it’s something similar to the commandline under windows. at least it’s comparable.
maybe you would run a docker, snap or vm on your webspace - that would make it a bit more complicate.
perhaps you would want to try this addon for your nextcloud? i haven’t tried it myself but it looks as if it’s giving you shellaccess. awww. and you could do some damage there. so pls be careful on what you do… and take backups!